Optimal front wheel back space?

[Apogee]

Assuming it's the same as a '73/'74, my vote would be 5.125" to 5.25" backspace, otherwise you're going to be getting friendly with your outer fender lip with a 2-3" drop. You should be able to get away with less BS if you roll the fender lip and maintain a slightly tighter turn radius, however it will depend somewhat on your static negative camber numbers as well. A 255/35R18 is fairly short at 25" diameter, so that should only help. Our 245/40R18's mounted on 18x8.5 wheels with 5.06" BS rub slightly at the steering box just prior to full lock IRRC, so we built up the steering stops slightly...still have yet to hit the road with it though.

Tobin
KORE3