ive got a 63 Belevedere 3 on tree two dr hardtop and some questions, not to be the last I'm sure. I've aquired an OD 4 speed and curious if this is a direct bolt up or are modifications necessary? On the old rear end, it's the nut on the end style and without the correct tool it's a fun job getting the drums off. I rented the right tool. Will a later model 8.75 fit right up or will I find issues that will need to be addressed? Thanks for any and all replies.