All 17X8 Mustang wheels have a +30mm offset.
Those wheels will fit a fox 5 lug conversion. But the centers will only fit using 94-94 or 96-04 spindles.
Ryan218, used those wheels and Mark VII stuff, but he had to use a spacer, grind the inside of the center cap, and bang in the dust cap.
Don't go with a Mark VII swap. You still get crap fox brakes. Upgrade to 94-95 sindles, with 99-04 GT/V6 dual piston calipers.