Been thinking of some 18's

[Riff Raff]

I'm thinking of mating these with some 35" x 12.50" x 18"...

See, you were originally planning on changing to 18" rims anyway with 35" O.D. tires. It's just that the narrower 11.50" width (aka 285 series) will fit much better (and look much better) within the smaller VX wheel-wells. Leave the large 12.50" width to the larger full size 4x4 pick-up trucks, for which they were designed.

Consequently, go with a LT285/75R18 (aka 35" x 11.50R18). If you want an "A/T" tread, you're choice is simple. If you want an "M/T" tread, you've a few picks.