running a 1"/front and 1.25"/rear spacers on my car with 94-04 17x9 bullitt wheels and 245-45-17 tires if that helps...
i have 1inch spacers in the frt and 1.5 in the rear. and 1.5inch in the rear. i have the larger ones in the rear because im running sn95 cobra spec wheels and tires..245/45.17 frt 275/40/17 rear. i used 1.5 spacers for clearance of the leaf springs and because i wanted to have the fenders rolled enough where the wheels barely tuck inside. i must say it looks kick azz! and i know.. the tire is on backward! lol i just had it on for fitment purposes at this point
if it helps, my buddie had stock 6 cyl 03 stang wheels on his 3000 gt and they fit like a glove. so id say 1 frt 1.25 rear
here's my specs.... Size:17x9 Centercap Size:Large (2-1/2") Back Spacing:5.94" (151mm) Offset:+24mm (0.94") Bolt Pattern:5x4.5" (5x114.3mm) Fitment:94-04 V6, GT, Bullitt, Mach 1, and Cobra