64 rear end help

so i switched my front to disk brakes (which was a pain to figure out the right stuff) and now the front pattern is 5 by 4.5" while my rear is still 5 by 4" so i am trying to figure out how to chang that. i belive i have a 7 1/4 rear end so i am trying to switch it to an 8 1/4 or an 8 3/4 but i am having trouble. i know a guy who has a 8 3/4 but with no axels and i know it will be to wide so is there a way i can shorten it? any help would be nice and i am grateful for anyont that will give advice:cheers: