I don't know the details of the trailer you have in mind, but your truck should handle it.  You'll need to install a gooseneck hitch, look at the B&W turnover ball.  It seems to be the most popular. 

Search the postings here for information on how to determine the amount of trailer you can pull.

One other consideration, since you have a short bed pickup, make sure the trailer has a tapered nose, if it doesn't clearance between the trailer and the truck cab will be an issue when you make tight turns.

I pull a 3H gooseneck with my shortbed Ram 2500 with no problems.  I do have the Cummins though.

"Mechanically the same.."  NOT .... I'll assume since you want to move up to a four horse trailer from a three horse trailer, you're gonna haul 4 horses.

You will find your 1/2 ton truck will be lacking in the weight carrying area.  Also known as payload...  The GN will put about 20% of the trailers weight on the hitch.  Without real numbers, I can only guess,  My guess is you will be severely overloaded with the hitch weight of a loaded 4 horse gn.  Remember the weight of the hitch installed in the truck counts toward the payload too.

The tires, springs, wheels, frame, brakes, shocks, of a 1/2 ton truck are not up to the 4 horse GN.  Look up the ratings yourself.  Don't rely on the faceless musings of the internet truck jockeys that fancy themselves experts.

edited for spelling

By common usage:  started before I was even driving.

class 1 trucks = 1/2 ton = ford 150, gm 1500, C10, etc

class 2 trucks = 3/4 ton = ford 250, gm 2500, C20, etc

class 3 trucks = 1 ton = ford 350, gm 3500, C30, etc

Chadsalt:  If a 1500HD was not a class 1 truck, GM is either marketing through their teeth or lying.  It's all marketing.  Would you compare a Ford 350 SRW to their 350 DRW and call them the same?  I'd wager if it was truely within a current class 2, they'd change the series number and charge more.  Your pick...

"internet truck jockeys that fancy themselves experts"....and I are one!

Harfy....see what you started!...If I had no uptruck choice I would get a 4 horse G/N stock combo trailer . keep it light!!!...I personaly wouldn't want to haul 4 horses people and gear very far! If you want a fancy trailer with drop down windows and a weekender package...well you know what to do spend $$$$$$$$$$ on a new truck!

Okay .. It seems like GM is marketing a 3/4 ton truck as a 1500.

Harfy:  My advice advice still applies. investigate your payload yourself.  Realize the stated payload is for the base truck.  Subtract the weight of passengers, optional equipment, gn hitch, hay, firewood, etc to see if you have the capacity for that 4 horse trailer.  You'll have to make a judgement on how close to the max you're willing to risk.

Chadsalt: To paraphrase Sir W. Churchhill... I stand corrected this afternoon, you Sir, will still be a faceless internet truck jockey that fancy's himself an expert in the morning.

i do what i can. 

Unless things have changed over the years (my truck is a l978 4WD, I disagree on the size of the brakes being the same regardless of the truck series.

However, it makes the most sense to me to ask the moderator of this board; unless it isn't the guy at the top with the handlebar mustachio that sells trucks and trailers for a living.

My '78 GMC was born a heavy 3/4.  It's been modified to have one-ton cargo van leaf springs on the back end.  I had a '73, 454 out of a Suburban modified and put in after blowing up two 350's trying to haul a 4-horse stock trailer around in the Allegheny Mountains.

2003 models aren't near as Backyard User Friendly as my old GMC.  Might want to think about trading it off for a 2500 series with the appropriate towing package.

Unless you already have a big block in that 1500, sure you can haul the gooseneck around all you want on the Flatlands with a small block.  Too much hill climbing, especially loaded and in the heat, might get you blown up -- motor or transmission or both. Might just burn those brakes out too.  I did that once on a '73 3/4 ton that WASN'T heavy duty.

No matter what's being discussed in this life, "there ain't no replacement for cubic inch"

things change every few years and if youre dealing with info from 1978 i dont see what you intend to add to this discussion.  i fail to see why you would disagree about the brakes, you apparently have acess to the internet. you do realize were talking about the 1500HD? and what would make the most sense is to check with the manufacturer. click on the braking tab and see for yourself.

http://www.chevrolet.com/silverado/specifications/#trailering

and youre right, "there is no replacement for displacement." except a turbo....wait, wouldnt that change the diplacement....oh never mind.

Harfy-We had a 1/2 T Chevy and pulled a 3H GN Steel Towlite.It wasn't enough truck for it,the tranny went.The truck was old,but still wasn't enough.Finally 4 trucks later(long story) we got a truck for a trailer.Might add,we also traded to a big LQ trailer,hence,# of trucks.

Also may I add something about the turnover ball hitch? We had one,and you MUST be diligent about reversing the ball hitch and keeping it clean and lubed or it will "freeze" and will have to be hammered out.I like the "Hidden Hitch" where the ball hitch folds down rather than having to remove the ball and turn it over when not in use.The clearance on those is just too tight and if any grit or dirt at all get in it,forget it.You can't get it out.

things change every few years and if youre dealing with info from 1978 i dont see what you intend to add to this discussion.  i fail to see why you would disagree about the brakes, you apparently have acess to the internet. you do realize were talking about the 1500HD? and what would make the most sense is to check with the manufacturer. click on the braking tab and see for yourself.

chadsalt, I respectfully reply in kind:

You are correct that I am dealing with a 1978 vehicle.  What I INTENDED to add to this discussion was a double check of things to consider for safety if the 2003 model in question is being modified.

I did not waste my time going to the spec website you offered up.  It was much easier to have my husband look up what I wanted to know when he got to work.

My original comment was that, "--unless things have changed---", which evidently they MAY have.

The 1978 1500HD came with STD 11X2 brakes. There was an OPTION to buy the 11-5/32 X 2-3/4 brakes.

The OPTION on the 1500HD series is the STD on my 2500HD series truck that I own.  The OPTION in 1978 for a 2500HD series would have been 13 X 3.

Soooo back to my original point, which I'm not looking up because I know you will and will be sure to let me know:  Does the 2003 1500HD model have a STD brake pkg AND an OPTION brake pkg.  If not and it's the same size as the 2500HD series, all well and good.

If there is an option package, it would be handy for the Owner of the 2003 1500HD to know if the truck has that package or not.

If the 2003 model follows the same philosophy as my 1978 does have an option package, it's OPTION for a braking system would be my STD on my 2500HD.

So, if anyone's paying attention, I certainly have contributed something, provided they care about why one and one equal two in the safety arena.

I do care about those "whys" because I worked for mechanical engineers that built power generating equipment, and am more than fortuante to have an ace mechanic for a husband who has also built some pretty healthy engines for Stock Eliminator and Bracket racing. 

I don't just take the word of a spec site on the internet.  Along with there being "no replacement for cubic inches", there's also no replacement for "good ole boy knowledge", INTRAnet, and old mechanic's manuels.

interesting, and thank you for clearing that up.

I'd get a bigger truck.