Just to confuse the wheel and tire issue even more; sometimes Pantera owners have tire rubbing problems and it has nothing to do with wheel offset and tire size/manufacturer at all. It's caused by simply having aftermarket shock absorbers. The Pantera's suspension travel is limited by the shock absorber. The OEM shock absorbers have less travel than most aftermarket shock absorbers, even though the overall length is about the same. If you only have rubbing when the suspension compresses and you have aftermarket shocks, it can usually be eliminated by installing an additional bump rubber in the shock absorbers.
I have 18"x12.5" rear wheels with 335/30-18 tires and height adjustable Koni gas shocks (from Pantera East) on my stock bodied Pantera. Initially I had a rubbing problem with the inside of the tire rubbing against the upper frame section. After installing an extra bump rubber, I have ZERO rubbing and the rear suspension feels no different than it did before.
Credit for this tip goes to Dennis Quella.