Changing the full rail is the best option. No repros are made. As the previous post said, any 67-76 rail will work, but there are some changes, such as the hole in the brake hose bracket and the 74-76 rebound bumper brace was updated. If your inner apron is in good shape, you can leave it in place, and just change the rail, or you can change the rail with the apron attached, from a donor vehicle. It isn't too hard to do, but you will want to drop out the K frame, engine, interior etc to gain access. Block the car well at the torque boxes- end of the rockers.