Borg Warner T10. Probably a Super T10.
The 1B is nothing more than a P/N for a main case. 1 designates main case. B is probably a revision number.
The 7A is a P/N for an extension housing.
10 spline input and blue paint is most likely Ford.
S10s were used by Ford and AMC from 1965 to early 70s.
Ford then went to their in-house Toploader.
GM used ST10's again from 1975-73.
You might send pics to Paul Cangialosi at 5speeds.com for ID.
Muncie M22 has a 20 degree helix angle making them noisy. That's why they were called rockcrushers, not because of their strength.
