I used disk brake spindles from a 70 GTO along with the calipers and 2 piece 68 Firebird rotor. I believe the Grand Prix and GTO use the same front suspension with front steering versus the rear steer in our Firebirds. But I believe there was a change in the calipers in 73 to a one peice rather than the ones with the removable steering arm. If that is the case, the 73's wont work. The calipers and maybe the rotors are the same I'll bet.
