The only thing I can comment in is your truck WILL be to high for a standard 5th wheel.
I had a 1500 96 4X4 with 265. 16's on it (I see your tires are larger?)
You can adjust the level of the 5th wheel plate to lower the front of the camper, but it decreses the distance between the bottom of the camper overhang and the top of the rear truck bed.
I "could" tow the 5th wheel with my high (stock) 96 but the bed to trailer clearence was very low (maybe 3 or 4") and I did hit the bed corner on the camper one time, but thats all it took to scratch the hell out of the truck corner.
Even with this low clearence the front of the camper was pretty high (out of level) in the front which did cause sway at times. (5th wheels normaly don't have any sway)
I ended up getting these kits from Dexter that allowed me to mount the trailer axles under the springs of the camper. this gave me about 3-4 more inches of trailer hight which fixed the problem.
To make a long story short, remember the RV dealer will sell you the camper anyway saying "we see these things towed out of level all the time" and they do see it all the time, but its not right!
Make them put the Dextor kits on for you to raise the 5er as part of the deal. If I am not mistaking, Terry may have several bolt locations on the spring shackles to raise the camper, see if it does and have the dealer raise it for you, But let the dealer know if that's not enough they will add the kits for you.
In 96 the kits were around $25. 00 per axle, but the can be a ***** to put on as you have to jack up the camper to lift both axles off the ground, its only time and if its the difference between a deal and no deal they will go for it!
Just a note: You will read about people "turning over the axle" one can only hope they really mean they are moving the axles under the spring and rewelding on the spring perches.
The RV axle has a spring affect to it, and the wheels will actualy be cambered in at the bottom with no load on the axle, if you actualy turn the axle over the tires will stick out at the bottom like an old VW bug with 2 fat people in the back seat!
I saw one the guy really did "flip the axle and turn it upside down" man it looked scarey how bad the axles were bent. You could see the bottom of the tire was about 2" out further then the top
Something else, you want the hitch that rocks side to side as well as front to rear, I have the Reese 20K classic and love it! I have had one side of the camper up on 7" of blocks to get it level and still been able to un-hook, and hookup when I left because the hitch can pivet side to side.