Let's see. A 22 foot hart with a 6' LQ.. Probably a 3 horse in that length. I suspect you will will about 13,000lbs loaded.

25% of the total weight on the pin will be 3250 lbs on the gooseneck ball.

I suspect that you will be really close.

But hey lets talk about all the neat stuff you can do with Air Bags.

the fellow that bought my trailer last summer, backed up under the hitch, using a back up camera with a DVD screen in the dash. Stopped at the perfect spot.  Hit his air bag compressor and lifted his bed up until the ball connected. Hop'd out of the cab and raised the jack.  Put up his tail gate and drove off.  Says he does the same thing with bumper pulls and a second camera in his bumper.

Now I'm not that technology up to date.  But I did use my air bags to lift my trailer higher to give me extra clearance for the black water tanks when I'd get in some rough stuff.

So regardless of whether you need the additional load capacity, The air bags can help, level the truck, raise and lower the bed as needed.

The following is a previous posting to a similar question:

I'll be the "odd man out".... Seems to me if you're having to add extra springs (air bags, timbrens, helper leafs, etc.) then you are a little shy on truck to begin with....

Flame suit on, light the torches!!!

As a kid in the late 60's we bought cars and jacked them up. I remember learning about problems this caused. I can still hear my dad telling me  " Detriot spent millions to design that suspension and you spent $5 at the corner parts store to Screw it up"

I'll agree with Retento.  Air bags are not going to increase your trucks load capacity.  If your truck is not rated to carry the load capacity, Buy a bigger truck.

If your trailer weighs to much for the springs, it's probably also over capacity for the axles, lug/lugnuts, tires etc. Adding air bags to help the springs out doesn't strengthen your axles or bearings etc.

But airbags do add some versitility to what you can do with a truck. I run my airbags at 15 psi. So they barely affect my stock suspension.  But as I mentioned, if I get in place on a forest service road where I'm going to drag my sewer system under the trailer over a rock in the road.  I can gain an extra inch or two of clearance by boosting my bags to 70 psi. And ever since I watched that fellow pick up a trailer with an air bag, I've been sold on not having to crank a jack up or down in order to hook up a trailer.  I hook up a flat bed equipment trailer, a dump trailer almost Daily. Some times several times a day. In the winter when it gets muddy and nasty on construction sites. It's so nice to back up to a trailer to the perfect spot on the first try, inflate the air bags and pick up the hitch with out gtting my feet  in the mud.

Same thing with my horse trailers.  Pull into a camp site. Not quite level, inflate the air bags and help level the trailer

Now in order to do this you need the optional compressor in addition to the standard air bags. But this also gives you a onboard compressor to inflate flat tires, inflate air mattresses etc.

I wouldnt go that far, seems like these late model 3/4 and 1 ton pickups are softer sprung than the ones I used to drive.  Too much double duty I guess.

chad... Seems like the late F250 and F350's are the worse. Several friends of mine have them and they all have added some type of aux. spring. I guess alot of the F350's 13000# GVWR is up on the front axle. I have backed under heavy hay trailers that leveled my 3500 Chevrolet out, my buddy backs under with his F350 and the head lights are aimed up in the trees until he get the wind back in the bags.... Unloaded My truck rides better that his..... Go figure.

If you are buying them just to raise and lower the truck to hook up.  You will be better off installing a electric or hydr. jack....  I had a set on the 97 F-350 I just sold and it would raise and lower the rear about 2" or so but not enough to help with hooking up my trailer.  The set I have on my 07 Dodge only raises and lowers the rear maybe 1" total....  I would install them for a more stable ride while loaded and not as a hitch helper.

Not the fact of being a little shy, it is all about a more stable ride.  Anyone that knows newer GM trucks knows that there springs are softer than most other on the market, that is why when you hook up a trailer most set down on the overloads right away.

I tested this myself on Wednesday, sister inlaw has a 2005 Chevy 3500 extended cab daully D-MAX with 25-k miles that I was doing service work on and I thought I would give it a try since there has been so much talk on here about them and I have never drove a D-MAX loaded.  The Sundowner in my picture is a 2004 8010 Signature 3 horse and weights around 9000-k or so.  As soon as I drop the trailer the truck rear springs went flat.  Drove down our FM road about 9 miles to the interstate and came right back home.  Truck has good power, transmission is the best, but the brakes (or whatever GM calls them) are MAJOR LACKING in that department, to say the least!  Had to set my trailer brakes way up to stop this package and I was unloaded.

If you are not buying the airbags for their load height adjustability, you might consider the Timbrens. They do not change an unloaded truck's ride. They require no maintenance, plumbing, compressor or adjustments. They always provide the exact load ride height you choose, regardless of the load's weight. They eliminate spring swaying when hauling, and will not allow a heavily loaded suspension to bounce or porpoise when going over a wash board surface.

I can always count on the same ride height and the truck's attitude, regardless of which trailer I tow. There are no headlights in the sky when hauling, nor wash board jitteries and a harsh suspension when empty.

Installed, they are a fraction of the price of airbags and a compressor. I've had ours in service for many years, with absolute reliability and with no maintenance needed. I would not consider hauling with any truck, without their installation.

Gard

I would check around on prices, the ones on my 07 Dodge was $350. without the compressor.  The compressor is just up to the person.  I have never installed one and really never had the need for it.  I check them everytime I fill my truck up along with checking the tires and keep 70psi in the bags all the time, this seems to work out great for my setup.

As far as holding up, I have had 4 sets and the only problem I ever had was on my 97 F-350 the retard that installed them mounted one backwards (they have mounting holes for different trucks) and the frame rubbed a hole in the side of the bag.  But I guess that wasn't bad, they had over 100-k miles on them before that happened.

They will leak just like tires, mine avg. a few pound per month, before I started checking them every fill up.

I have Timbrens on my pickup.  Timbrens are a rubber spring that is larger than, and replaces the factory bump stop.  They are cheaper and simpler than airbags, although they can not be adjusted like an airbag.  Take a look around their website,  http://www.timbren.com/timbren-application-guides/chev-gmc.htm

Mr Truck also has a write up on them,  http://www.mrtruck.net/timbren.htm  His truck was a Ford but there is little difference.

Your 99 probably takes the same kit as my 05.  They work well, but they will affect the empty ride.  When installed per the instructions there will be ~1" gap between the Timbren and the axle..........the axle moves more than 1" when empty in normal travel.  When the 1" is used up you will hear/feel the axle contact the Timbren.  Some people find it objectionable, I dont care the truck rides like crap anyway.

Here's some photos, product availability and pricing. My Timbrens have a 6k# rating, my factory over load springs have a few hundred pound rating.

http://www.buyautotruckaccessories.com/product-auto-apps.cfm/cf-bin/pn.timbren-suspension-kits/?gclid=CNa_w8HKhZgCFQpuGgodkW4RCg

And here's the company glib about them;

http://www.timbren.com/

Which kit/what year Ford do you have that allows them to be "set"?  My kit allows for ~1" or zero clearance. 

While my statement may be "untrue" in your case, she appears to have basically the same truck I do......so you may see the relevance of said statement.

The set I have on my wrecker that have adjustment holes to preload the helper spring if needed.  I have them set with about a 2" gap when unloaded, so when I put a truck on top the wrecker will just touch the Timbrens, then when I load a truck on the rear is when they really cone into play.  Or I can change holes and set them to make contact faster if needed.