Considering you are still running the 170 (according to your salutation) unless the 7.25" is howling or failing in some other way - which can be hard to repair due to the woeful availability of parts for it - you should just run it or collect a few more of them to act as a stock-pile to replace them as they fail, or to build the best of a few. I see more of those offered for free to nothing than any other rear-end out there.

There are a few of us who have installed the 4-lug 8" without any modification, but that 1/4" on each side if it were to be a problem could be assuaged by rolling or trimming the rear flare to take the edge away.