i run P235/70R15 on 86 trans am 62" wide rear axle, similar rear axle to yours
first off you are running extreme deep dish wheels with little offset, i believe mine are 4'' offset
second you have no tubs to run that wide of a tire, consider mini-tubs in the bedsides
truk is on stock springs and stock spring hangers, with the axle flipped on top of the springs
your wheels look at least one inch less offset than mine
granted i don't have much space between the fender lip and tire, but it never rubs
to change tires i have to jack up the frame, remove the lugs and wiggle the tire out from between the fender lip and disk brake
it works