Cant fit front center caps on...Any suggestions..?

Sounds ike the rotors may be from a Mark VII.Perhaps different rotors.The Mark VII's have a longer hub.

Yes, it sounds like you have the cheap & easy conversion, Mark VII rotors. It is not just the rotors themselves, but the actual spindle design that is longer. The Mark VII rotors/hubs fit and are the same as the stock ones, they just have an extra wheel stud.

If the caps barely won't fit, you can try to flatten the dust cap. If you didn't have 9" wheels, a spacer could be an option, but is not recommended without hardened wheel studs. A spacer might be too much with a 9" wheel.

Best option is to use 94-95 Sn95 front spindles and some rotors and calipers that fit it, 94-98 stock, 99-04 PBRs or Cobra style brakes.

Read the Brake /5 lug conversion info on 87-93 Mustang 5.0 Brake upgrade pages. Improve your 60-0 times! for more info