The Search Function on this site will help you alot on this topic but here's my .02 from reading a bunch about this:

Without doing a lift I believe the largest diameter tire you can use is 31", this still might require a little trimming on the front cladding but that's easy. Nitto makes the Mud Grappler which is probably one of the gnarlyest tires I've seen with sidewall tread.(swampers are cool too but very heavy and will suck the performence outta your VX real quick). Hope this helps.

On a related note: Can we do 32" tires with just the torsion bar crank and ball-joint flip or do we need the rear lift springs too?