Late model mustang wheels on early A's?

The big problems are back space and the inner rim hitting the upper control arm, at least on an 18x 8.5 with 6.3 back space (2006 GT rims) on an early A. I have the 18 x 8.5 rims on both ends, with a 225 x 40 front, 255 on the back. I had to move the springs into the frame rails and use a wide rear out of an Explorer out back, and a set of triangular A arms up front to gain room for the inner edge of the rims. The fronts fit great now, full turning radius, the rears are maxed out and have 1/2 inch clearance in the tubs both inside and out at normal ride height. It gets tighter down lower so lowering the car with 255s is not a good option.