8 3/4 help needed

Kind of a noob here so please bare with. 72 dart custom (4dr). So my local junkyard is having a half off sale this weekend so I wanted to go look for a 8 3/4 diff, currently have 7 1/4. What donor should I look for? Does it matter? I'm hoping on a sbp since that's what I currently have (new wheels and tires). Would converting a lbp to sbp be easy, in case I only find a lbp. Perches can be relocated if need be right? I know I'd need the u bolts and plates, is there anything else I should know? Thanks