7 1/4 to 8 3/4 rear end swap

i have a 73 duster with 318 and 727 trans and would like to change the rear end from 7 1/4 to something bigger like 8 3/4 or 8 1/4 i have never done this before but sure i can, what would i need to complete swap other then rear end, and would 8 1/4 be better than 8 3/4 this is for street use only just affraid the 7 1/4 in it is to small? thanks for any help