My 2 cents:
Chassis - Design something from scratch and build it yourself...would be half the fun
Wheelbase? 116" Big rubber means you want a long wheelbase.
Engine Lexus V8 - cheap, light and can produce serious HP. Mid mount would be ideal - but then WTF do you sit. I'd probably go traditional Front mount (I don't like the idea of a big fat lump of metal sitting behind me if there was a chance of a sudden stop
)
Although something smaller would be nice.....
Diffs Mogs would be my budget pick, something like the PSC HiMark or the sunray 9" hybird portals would be my pick.
Suspension Nope would still go airbags - but a little different again
Linakages probably just a 4 link F&R.
Gearbox & transfer 4spd is useless for a buggy....So I'd probably go something like a TH350.
Transfer case - definately Stak.
Wheels 20" and bling ones at that.....I'd go staun internal bead locks (since mud isn't likely to be an issue).
Tyres Either Irok (mixed surface) or MTR (sharp rock) Absolute min 40".....
I definately would not go 15-17" rims as I think under throttle and on side hills there's too much sidewall movement.