Thanks Steve for what I would need to do in order to make it work. I was hoping it was along those lines of swapping out the backside. Pricey and scarce parts may kill the deal, and I may just look around for the right vintage unit instead. They pop up every now and then, but shipping is a pain/expensive and salvage yards in my area have no idea what I am talking about when I go looking... I've rebuilt the 3 speed shift box, replaced the bushings, made sure the levers were parallel and adjusted the shift lever clearances per the manual, but it always starts hanging up once the temp hits 185 degrees. Every time I think I have figured a way to fineagle it into working, it always lets me down. I'd be happy slapping a hurst floor shifter on it just to avoid all those troubles.
Gord and Sstock, good catch! I misread the ad... I just looked at it again, and it said that it came out of a 71 chevy pick-up, but was a 1960's SM420 unit. The casting code is 3896779 (picture is below), which probably aligns with your thought of it being a 67 because of the backup light switch.
