Your rear end is likely a GM 8.2" ten bolt. The Ford 9" won't "bolt in". If you are capable of narrowing it, you'll have no problem doing the measurements needed, along with welding on the control arm mounts and spring perches. We can't answer your questions on width, you need to do your calculations based on the offset of your wheels. There's really no reason to swap in a 9" unless you are going to put down some serious HP, and running 26s, I doubt that will be a priority.
Two doors, four doors, wagons, and ragtops.