I turned my 8.25 (8 1/4) rear into a sure grip.
I think I used an Auburn gear. I was also able to find a 3.21:1 ring gear for a slight upgrade as I didn't want to get too radical and keep highway RPMS down.

Just find a reputable guy that does rear ends (I found a mopar guy that works at a tranny shop up here that many go to). I bought all the needed parts and gave them to him to install. The only problem you might need to contend with is the application coverage for the rearend bearings and such as I think the 8.25 rears 70-75 is one style and 75 and up is another style so make sure your 8.25 hasn't been changed if you go this route.

Unless your 360 is pushing over 350 Horse power, then stick with the 904 and beef it up a bit. Just a suggestion.

Mine is a 360 with about 300 HP and the 904 is a slightly better than stock rebuild and the 904 tranny and the 8.25 is holding up fine. I also added a tranny cooler to it for piece of mind, and it keeps it real cool in summer months.