Rear end question

Ok, I have a 64 valiant that has an 8.25" rear end that has been whiney for the whole time i've owned it.

The rear is a 8.25" 1974 dart with shuregrip.

After the 5.2 Magnum swap, It broke one of the carrier bolts. I discovered that the yoke nut loose and I replaced the bolt.

Now its whining bad, when at speed if you lift a little, like between acceleration and deceleration, it starts whining BAD!

It doesnt do anything bad on full accell or deceleration.

The mechanic I'm working with says the ring and pinion has to be replaced (he rebuilds big time diesel rears, so I hope he knows)

My question is Whats the best route to go? Ford 9", Mopar 8.75, Dana 60? I have the shurgrip center chunk that seems good, the 8.25" Housing, new axle bearings, Disc brakes, and BBP.

What way should I go? Rebuild current ring and pinion ($1000) or buy another rear end all set up and replace brakes, spring perches and cut length / axles ($????)
:banghead: