Sorry, I was unsuccessful loosening the drive on the car. I pulled the upper seal and kept it flooded with penetrating oil while letting the motor try to work it in. Could not budge it from the top side. Once I disconnected the drive from the motor, I was impressed with the power that gear motor develops, after needing a lot of force with a leather-gloved hand to twist the drive pulley.

Once on the bench and in the vise, the struggle was still no pushover. I dug up a drive from an 83 I'd saved, figuring I might ruin the later one I had, but it was not a direct match. I know there are at least three versions, having a 79 like yours and two later ones.
















--
Art Benstein near Baltimore

When a clock is hungry, it goes back four seconds.