18x12 with leaf springs.

[1971gmcshortbed]

Hello forum, I haven’t been here in years. I still have my project and I’m trying to see if I can fit 18x12’s in the back of a 71 short bed. It will be pretty low with a static drop. I’ve searched and can’t find anything conclusive. It’s a fleetside and it’s taken apart right now. I have a bed with coil springs to measure the fender clearance but not the leaf clearance. Does anyone know if this can be done with leaf springs? The tire is a 345/35 18 and I’d like to tuck it in the fender an inch or so.

[1971gmcshortbed]

After some measuring with a coil spring truck I figured out 7.5" backspacing. I did find other people that used this backspacing also.
I made sure my differential and the coil differential were the same width, then I mounted a wheel on the test truck and measured how deep the wheel is on the axle. I transferred that measurement to my differential and was able to make sure the 18x12 would fit. The turnaround from Boyd was only
2 weeks. The wheels are a little dated but it beats buying 4 wheels.