I have this trans and I think it's a SM420, but not 100% sure. On the pass. side it has a large rounded hump and on the driver side of the trans is this number GM 3837834 and on the top cover on the driver side is this number GM 17 T 3895779. I have pics hosted if it's OK to post the link up for this trans.

THANKS GUYS

Posting a picture would sure help,

Sounds like an SM420 to me. Super, low 1st Gear (7.05) hella strong. Does it look like this?
310466
http://www.novak-adapt.com/knowledge/sm420.htm

1964-1967: Same as previous except 1st-2nd synchro ring is aluminum and 3rd-4th synchro rings are identical to each other. Seven digit casting number usually like "37xxxxx", "38xxxxx" or "39xxxxx".

SM465 has a large cross cast on the side and the top cover is different:
310467

Yeah man thats the one:spam: thought it was a SM420 but wanted to be sure :homer:

A 420 will have a big bump on the pass side of the case near the rear and 1 pto cover and have a case that is 10'' long. The 465 will have 2 pto covers and have a case that is 12'' long