Rear end mounting question

Unless you want to reweld the spring perches and have to deal with getting the rearend centered, pinion angle, etc. I would just look for an A-body differential housing. The 7.25" will last until you find something as long as you dont beat on it too much. If you do want to weld on spring perches, the 8.25 from an XJ or a ford explorer 8.8 are solid options.