Pushbutton trans parts interchangability?

Hello. I found a 904 from a slant six 1968 Dart for sale locally. It's cheap enough so I'll probably get it. I have a 1964 Dart and I know that the pushbutton case and atleast the valvebody is different in later column/floor shift 904s. There may also be output shaft differences since 1964 was trunion type output and I think they were open drive/u-joint style by 1968. Anything else I should be concerned about?