The holes in the glass are spaced differently in the earlier cars. It should work IF you have the track that attached to THAT glass. You only need the piece that has the blue or green retainers that hold the glass.
Don, It is the 76-77 glass that throws a wrench in the spokes...different spacing in the holes in the glass...different holes in the door itself to mount the regulator's support arm.
Yep...Been there...got the T-shirt. I still think a 1952 Packard regulator might would had fit better