I am looking for an 8-3/4 complete rear-end, or a housing with axels,or if I have to all seperate compenents, etc. As I look though I see ads for small bolt pattern, large bolt pattern, Housing with-out axels, third member only 492 case, 481 case, etc. I am confused!

I have a 1972 Staellite Sebring plus that I am putting a 440/727 combo in (I am removing the 318/904/7-1/4 set-up). My question is what exactly should I be looking for? Bolt pattern? width of axels, case #, sure-grip unit #, ring and pinion set up for daily driver, etc. I know A-body rear won't match up but what about C body or? Any direction would be appreciated!