I agree with Bill. I don't know of any way to differentiate between car and truck trannies other than the part number. And then that could take a buncha research. According to my Chevy By The Numbers book for 65-69, there were 23 versions of the 3-speed Saggy in 65, and only 4 in 66-70.
Incidentally, the 66-70 is supposed to have a synchronized 1st gear, something the earlier models didn't have.
The book also mentions that there was a Muncie heavy-duty 3-speed available from 69 to 72, but I've never seen one.
What that book doesn't provide is a list of casting or part numbers for the various transmissions. It's very lacking in that respect.
Sorry I couldn't be of more help.
