8 3/4 Rear End Question

New to 8 3/4 rear ends. I have a 741 case now with 391 gears. I can get a 489 case with 323 gears and sure grip. I would like to use the 391 ring gear in the 489 sure grip and put the 323 ring gear into the 741 case. Is this possible and if so any issues or anything to look out for? Thanks!