[Tx Firefighter]

71-72 had disc brakes and steel screw in control arm bushings.
73-87 had disc brakes and rubber control arm bushings.

73-87 upper control arms have a 3/8 hole in the front of them for the brake line mounting tab to screw in to which 71-72 do not.

71-72 brake lines run across the crossmember and mount to tabs on each side right in front of the crossmember.

73-87 brake lines did not run across the crossmember at all. They ran down the inside of the frame rails.