Hello transman, the transmission is a 904 1971 non lockup, the converter is a boss hog pn 53023. I have a 42re here and the oil pump is exactly the same. Even the oil pump shaft.
I'm not as familiar with the newer transmissions, but if the 42RE had a lock-up converter, swapping them will not work. Lock-up transmissions have about 3/4" of the shaft tip machined smooth. Non-lock-up has splines all the way to the tip.