Help - Inherited a 1978 C20 with SM465 disassembled

I inherited a 1978 C20 from my grandfather. He parked it about 25 years ago after an unknown transmission issue.

I've already got the engine running again (that was pretty cool to fire it up) but now need to get the transmission reassembled and put back in.

The issue is that he had the original SM465 2WD pulled out and disassembled. He also evidently had another transmission he must have purchased for parts, which is also disassembled. I'm not sure which internals went to which trans, and I do know that not all SM465s are the same depending on 2wd/4wd and slight changes over the 20+ years they used them.

Can anyone help me figure out which of these is the correct 4th gear? The one with the seal and plastic thing on it doesn't seem correct... but it's not chewed up on the tips of the teeth like the other one. Also not sure where it came from if it's not from one of the two disassembled transmissions, or where the other 4th gear went..

The speedo gears are also slightly different.. not sure which one is correct for 1978 c20 - what do I need to know - rear end ring gear?

Any help is appreciated.

No help on the internals, but since they are basically bulletproof and not rare, I would just look for a cheap used one. But good for you for using what you have.

Hi gijordan07.
When I rebuilt mine a while back this guy took you through step by step.
Site down with a beer and watch part 1 and 2.