94-04 Mustang wheels have a 5.72" backspacing.
05+ have 5.295" of backspacing
That means the backs of 05 wheels are 0.425" shallower.
When put on an 94-04 Mustang, they will stick out about 1/2" more than stock. You'll have to see if this is livable. 99-04 cars can pull it off but not sure about 94-98