Got Cragars, will this backspacing work or do I need to exchange?

[SkinnyG]

Based on the pictures, the rear tires tuck inside the rear fender - their tops are higher than the fender edge.

The tire sidewall will bugle slightly wider than the rim itself. This means the sidewall will protrude outside your fender, and the tread will still hit the fender edge.

A 295/50R15 is slightly shorter than a stock tires, but you're really going to want to have a minimum of 2" travel (I'm guessing) before the tire hits the rim, or ridiculously stiff springs to stop it from moving at all.

You might be able to roll the fender edge up and slightly -flare- the box side to clear, but it's going to take work. (I did this with my last truck, a Nissan Hardbody with Toyota Tundra steelies - the sidewalls were getting cut by the fender edge).