I think the trans might be a rocker crusher because of the C. Does the trans. have a vehicle code? Maybe it was a factory replacement for your car under warranty. I think in 1970 the M22 went to fine a spline input shaft. (Not sure of date)What do you have? Sounds like a 1971 trans. case anyway. Depends on how perfect the car is. I don't think I would be over alarmed. Please fill out your bio!
JMO Sam