Hey Rad:

I believe these are Muncie transmissions. Couple things to look for:

Muncie transmissions have 7 bolts on the side cover (as opposed to 9 for a T-10). Snap a picture of the other side of these bad boys and I think you'll find 7 bolts holding the covers. Muncies can be differentiated from Saginaws as the the Muncie reverse lever is in the extension and the Saginaw is in the transmission case.

As to type of Muncie:

M-20 is a wide ratio
M-21 is a close ratio
M-22 is a heavy duty close ratio, also known as a "rock crusher"

Hope this helps,
Glenn