rear wheel backspace ?

[donthekawguy]

I'm just finishing up the front end rebuild and will be swapping the rear axles in a couple of months to 5 lug. I'm getting a set of Cragar Delux 69 in 15x10. The PO cut out the lip already in the wheel wells. I need to know what backspace to get the wheels in and tire size so they won't rub. I have 4 inch springs on it and might be going with a 1 inch block. Also I'm going with a 15x7 in the front and would like to know what tire size is good for those.