'73 Swinger brake drag

Are the pistons all the way retracted in the calipers? Could be an issue with the piston seals or caliper bores.

A digital caliper on the rotor will tell you if it’s the rotor, kinda doubt it’s the rotor.

On a disk brake the only thing that retracts the piston is the flexibility of the piston seal, outside of that it’s just the spinning rotor knocking back the pads.