I have an 83 pickup. I'm shopping for 5 brand new wheels for it.

Currently I have no lift. I'd like to run 31x10.5 for now.
The width range on BFGs website for that size is 7-9inches, and they got 10.5 section width on an 8.5 inch wheel.

Eventually I'd like to run some lift. Then I want to run 35x12.5s.
The width range on BFGs website for that size is 8.5-11inches, and they got 12.5 section width on a 10 inch wheel.

So I'd like to keep the same wheels as the truck progresses, and I'm thinking an 8.5 inch wide wheel will hopefully meet my needs.

Also, eventually I'd like to run an 86+ width axle and 1.5inch spacers up front... I've read that 3.75 inches of backspacing is about the max for stock, but I'm wondering what a decent amount of backspacing would be for when I'm stock, and when I'm running 35x12.5s with 1.5" spacers up front.

Right now, I'm thinking 3.5" would be ok... but I'm not 100% sure.