If your talking about the 10 x 15 and 13 x 15 Campys that came stock on both GT5 and GT5-S Panteras, the bolt pattern is standard Ford 5 x 4 1/2".
The backspacing to the outermost flange is 4 5/8" on the front and 5 1/2" on the rear. Backspacing to the beadseat would be minus 1/2" on each.
My stock '86 5-S had 3/8" spacers on all four corners.
Michael