I'm "the guy" who can't remember. Soileau, are you sure the "80" trans you have pictured is in fact original from the car? As far as I know, the early 5 speed (77-79) has two ears, and the later (80-83) is the other, and not just an 83.
BTW, the one that Mark's getting is the single ear one.
Mark, I was thinking if you want to know just to know, worse case senerio, after you put the trans in, just calculate out 5th by your RPM's and rear end ratio.
Phil