Wheels and Tires Drivng me nuts - What do you think

[tsetsaf]

Hey folks I don't post very often but do peruse often. Will soon present my retro-moded 71 at Hot August Nights in Reno. Gettin' down to the final parts and I have a big question on wheels and tires. The truck is a 71 3/4 ton that will sit at stock height (the back end will be level with the front). My goal with the wheels is to go about stock diameter (29-30") a bit wider tread pattern on 18" x 8.5" wide rims. Designed everything around a standard offset with 255/55 18. Now for the problems the only truck style tires in 255/55 I can find are P rated. Argh.

My questions for you are what rim/ tire package will fit right in this stock height truck. I want the rims to sit perfect inside the wheel wells.

Rims:
18.0x8.5 Chrome 8 on 6.5 -4(BSM) 4.53"
18.0x8.5 Chrome 8 on 6.5 20(BSM) 5.48"

Tires:
275 -65 -18 32.07" overall height Terra Grappler
265 -65 -18 BFG All Terrain 31"
285 -60 -18 31.4" Terra Grappler (11.2" wide)

Your guidance is appreciated.