My objective is to remove the torque tube style drive shaft and rearend and install a '69 camaro 10 bolt posi with highway friendly gears (2.73)'s. Wanting to stick with a truck style 4 speed (SM420, I thought I needed to get an open drive shaft style transmission .ie. '55-'67 SM420 transmission. I did purchase what I believe to be a '55 SM420.

OK, here's the deal... Upon scraping decades of dirt and New Mexico grime from my "54 1/2T with original SM420 4 speed transmission. It appears to me that I could just swap out the "transmission rear bearing retainer" with the one on the '55 and not have to swap transmissions.

Can someone shed some light on what may be my $250 and countless hours of cleaning 1955 "transmission rear bearing retainer"? Of course it is attached to what appears to be an excellent working transmission.

Thanks