'70-'72 used 2 piece rotors (hub and rotor held together by the lug studs).

'73-'74 E-body and '73-'76 A-body disc brakes interchange. This design originally used unicast (1 piece) rotors with different inner bearings designed to fit the newer (larger diameter)spindle.

'70-'72 splash shields do not fit '73-'76 rotors.

I sell spindle sleeves and caliper brackets so you can use the common '73 and newer brake parts on '70-'72 knuckles.