A lock-up trans will have about 3/4" of the converter end shaft machined smooth. Chances are it is a lock-up. The valve body and pump and/or front shaft has to be changed. I don't know the specifics because JW trans always did the conversion for me. There is a visual difference between 2.45 and 2.74 gear sets also. But I don't know what that is.

Converters do not interchange without the conversion.