Back in 1988/89 my neighbor in Toronto bought a 72 Lemans GT 400 4-speed from the original owner, his co-worker. We were expecting a Muncie but it was a Warner Super T-10. This was on a low mileage car from the original owner and it had not been messed with at all. I'm of the mind that Pontiac  M20s from 1971-on were the functional equivalent, aluminum case Warners rather than the Muncies. Of course the M22 was still a Muncie.

The ad says that he was told it was a Judge. No Judges were produced after 1971, plus the Judges in 1971 all had the 455 HO. It really doesn't matter; the big valve 400 with a 4-speed was a great combo in 1972. It would use a 3.55:1 rear, a corporate 8.5" 10-bolt. I have heard that the Oshawa-built cars would have actually used a 3.55:1 12-bolt type C rear, but then again Oshawa didn't build GTOs in 1972 (70 & 73 were the only years).