62 gmc k20

[jwsteffen@gmail.com]

Hey all- I'm a noob here. I just picked up a 62 K20 and it came with two Trans/TC combos (the original is an SM420 with a t221 m7 that is seized up). I'm working on getting things spinning in that again, but in the meantime, I'd like to make sure I know what I'm dealing with and what my options are. The Second combo appears to be an SM465/t221 N? Attachments are not working for some reason, but the trans has a 3901127 on it.

Anybody have any arguments against just using the 465 combo? The input shaft is different-- anything else I'll need to change out?

Thanks in advance for your help!
Jason