There was never a mustang II with factory 5 lug wheels. The pinto front end was the same and they were all 4 lug too. A popular swap was to use ranger rotors but you had to machine the diameter down to make them work. You can buy aftermarket 5 lug rotors for that front end that will bolt right on. You can get them in both ford and chevy 5 lug patterns. check with street rod parts supplier.