8 3/4 rear end help

You are going to have to be a lot more specific about the measurement. 4 ft wide from what to what? Is it complete length or flange to flange?

It was obviously narrowed, A body 8 3/4 rears are 52 5/8" flange to flange. It sounds like you would have to at the very minimum move your springs inboard and possibly mini tub. You also don't mention if it has the spring perches. Was it installed with a 4 link suspension or springs?

Not nearly enough info to give you any kind of decent answer.