As far as bolt pattern, if its 8 lug, then 1991 to 2005 e250's should all be the same semi-floating dana 60.
The e350's got a full floater, but I believe the width/mounts are the same, so you could in theory install that one also.
You might even be able to upgrade to a disc rear end, but probably need to swap the master cylinder out to handle the new discs.
Just watch out for cab/chassis dually rear ends. I believe their mounts are different, and they are a dana-70