Friend with 1977 camaro is getting wheels what backspacing?

can we fit a 15x 10 in the back without rubbing?

also what backspacings are ideal?

I have 15x10s in the back of my 71 w/4.875 BS running 295-50 Radial T/As. They rub a little on the fender lips on big bumps even tho I rolled them. There is a bit of room to bring the tires in to the closest point (shock body) on mine, so about 1/2" more BS would center it better in the wheel wells. A pic:

http://i67.photobucket.com/albums/h281/angel71rs/RS/RStiresRear.jpg