Torqueflite a904 slant six into a 74 318 HOW?

So my 74 Dart se torqueflite a904 has a crack in a couple bolt holes and leaks. I am thinking about buying and swaping an a904 from a guy who is parting out his 74 dart slant six. I have never attempted to swap a tranny and do not know if there are any swap problems. Is this a simple pull and plug or do I need to know that there is some different part on a 318 that is not on a slant six transmission or vise versa? Also were the a904's that went into a slant six car built differently than what went into a 318 car? Thanks Stay Gold