Wheel backspacing for guys laying frame

[baggedbigblock]

I am looking to get the deepest wheel I can and not have fender clearance issues. My C10 is on a raised and sectioned stock crossmember with 2.5" dropped spindles and currently has 15x? I think 7" wheels on 235.75/15. I notched the front fenders and when airing out it does hit the sidewall for 1 spot then the camber kicks in and it clears. The rears are fine. I would like to run Coker G78 with 15x8 or 15x7 smoothies. I am thinking I wont be able to get away with the 8 in the front but what is your recommendation. The G78 will be a more narrow tire.

Here is a pic to see how flush it sits now.



and standard backspacing etc I am not too sure on this. i deal with offsets on my dialy cars, I know backspacing is the same but in inches. I am just not sure what most guys are running, I dont want it tucked in.