Help with backspacing!! 20's

[gearheadmatt]

I've searched every word combination I can come up with and can't get a good straight answer.

Heres what I've got:
Its a 68 SWB with CPP 2.5" spindles and 2" springs.
In need of a rear at the moment but want to use specs for the narrow rear end.

Closest answer I have is somebody running the wider rear & 315's with 4.75 and some "massaging"

Wheels will be American Racing Salt flats, 20's. Need to order soon..
Wanting 255's front and 315's rear...possible without surgery?

[1stchevy]

Each truck is going to be different, the best thing to do is measure your truck. There are plenty of directions online just google how to measure backspace. If you need some help maybe lolife99 (Keith) would give you some direction.