I believe the older torsion bar cars had a plate rotor and the later coil over suspensions had vented rotors and Contemporary offered a dog bone kit to increase the vented rotor diameter from 10 9/16" diameter to 11 3/16" diameter.
I upgraded my vented rotors to the 11 3/16" rotors via the dog bone adapter.
https://www.englishparts.com/product...7/JLM776X.html
Mike