What Negative Wheel Offset is needed for my 1994 FJZ80?

[Rich A]

I ordered new tires for my 1994 FZJ80. I am going to put 315/70R17 BFG KM3's. I guess it is considered a 35" tire but technically it's a 34.36" tire. I'm good with that. A little fact, I saw a Ford Raptor with that same size tire but with BFG KO2's.
The manager at Discount Tire was talking with me about the Negative Offset needed for my vehicle. At first it appeared I needed a -6 offset but then he called Pro Comp Wheels and they said I needed a 17.9 (not sure if that means a rim size?) with a -12 offset.
Confusing???
Any recommendations for my rig with my tire size?

 

[smritte]

Im running the Fuel Anza rims with the same tire size. Their site is showing a 4.5 inch back space on an 8 inch rim. I think that's -16 offset. I removed my flairs and the tires just sit out about an inch. With a 2 inch lift (and a ton of added weight) I rub only on real hard bumps.

Scott