I have a 12 bolt in my '68. Backing plates are different but brake guts are the same. Axle tube to backing plate mounting pattern is different. I wouldn't think a set of backing plates would not be that hard to find. If nothing else, D&R Camaro has new replacements for $45 ea.
I used a shortened Chevelle driveshaft to mate the Turbo 400 and 12 bolt.
Rear brake line kit from The Right Stuff Deatiling for a '68 Firebird fit perfectly. I used the original (Camaro) 12 bolt differential brake hose bracket and the original style Firebird rubber brake hose. All worked and fit like factory.
