I thought they "fixed" the too narrow tailgate opening by now?.. my 92 GMC had it, as does my 96 Dually. Frustrating trying to load a camper that has the "bump out" where the bathroom is in shorter campers. I've found that the larger, 10 1/2' or larger campers are actually easier to load in these trucks as the "bump out" for the bath is outside the tailgate opening. That said, all ya need to do is measure that section and the tailgate opening on your truck.
Good luck! :)
Dak