Sure Grip Advice

While driving home from Carlisle, I noticed the whine from the rear end has got worse. It whines on acceleration. It is a 741 case 3.55 cone style that I bought here on FABO. I have the original open 3.23 741 from a 72 Duster 340. I want to go to 3.23 sure grip. Would you buy a sure grip for the open 3.23 and sell the 3.55, or buy a new gear set for the 3.55? Another option would be to switch parts from the two diffs. What would you do? Thanks FABO.
I would go with new bearings on the 3.55.
If money is no object and you want 3.23...then buy a new sure grip and bearing set for it. 741 is strong enough.