Hello .. Welcome to the forum .. I'm sure someone can answer your question.  But more information is needed about the trailer and Tundra. 

Trailer... how many horses?  LQ ? Length? Type?

The best thing to do is level the trailer, measure from the ground to the bottom edge of the GN.

With the truck measure from the ground to the top of bed side, directly over the axle.

You need to have about 7" between top of the truck bed edge and the bottom of GN. More if you drive over lumpy terrain. The worst is going into and out of fuel stops with the drainage gutters around them.  Some people go with less. I have a sloped driveway - going in and out, I use that 7"....