All the 1200 (including 1971-1973) use the JATCO transmission, model numer 3N71A. This is more or less the same as used in Toyotas, etc.

The B310 uses 3N71B. I'm not sure what the difference is, but I would expect it to swap right into a 1200 automatic car.

Hi,
I just had my 1000's auto box rebuilt and the difference between the "a" and "b" is that the "a" has a notoriously weak diaphragm spring on the first clutch which was strengthened for the "b" boxes. Mine was broken into three peices and it cost me $600 to get a chrysler torqueflyte one machined to fit! total cost of the auto trans rebuild due to damage from a neways additive: $1250.00.

But the auto rebuild bloke recons that these are still one of the best auto's around!