How wide can you go in the rear
 

I've got a 71 c10, mild built 350 4 speed Muncie. My truck is lowered and the bed and tubs are cut out so vertical clearance is not an issue here. I was wondering how wide of a rim can you fit on the rear of a c10? I have leaf springs with caltracs, axle flip kit with a 1 inch block, so roughly 7-9 inches lower than stock in the rear. My bedside fenders are rolled as well. I'm not terribly picky with brands of rims but the more quality budget in mind rims the better.

I know you can fit pretty wide rims without shortening the axle, which is what I would like to do. Factory c10 axle for note. But I would like to know how wide can I go without hitting the springs or frame? Diameter of rim, width, and backspacing listed would be nice, as well as a tire size to go with it.

I would like more than 1/4 inch clearance so I won't rub if I turn to hard or hit a bump. But still have the grip that a wide tire offers.

Not picky on material bit aluminum is always prefered