'64 Dart questions

I'm pretty sure the early 904 you have has a different spline count or something that makes the converter different. I don't think it's a big problem, just needs to be kept in mind when picking a converter. You might be able to have the input shaft changed during the rebuild, I'm not really up on automatics. Somebody here will let you know before long. Nice to have all of your ducks in a row before you start a project like this. Even if everything is right there'll probably be a hiccup or two along the way.