904??

Around the late 70's to early '80's, transmissions started going to lock-up converters. They can be swapped in, but need to keep the transmission and converters together because they won't interchange with the "regular" ones. Lock-up transmissions have the tip of the splines machined back about 3/4' on the converter end.

Not sure if '66 or '67 was the last year for transmissions with a small converter "snout" that goes into the register at the back of the crank. Needless to say, the sizes don't interchange based on the crank.