A '75 B-body car might have the larger 11.75 rotors. If so, grab the caliper adapters. If the rotors are good you might as well get them too. The calipers most likely will be junk but you can use them as cores.
I was hoping this would be the case. i scored my last set of 11.75 caliper adapters from this same yard for 7.50! the car had the 11" rotors and brackets. i got them anyways. i got every thing minus the calipers for 22 bucks. score!