The damage was done by the hop, as you said. So in addition to fixing what broke, you have to fix the hop. Pinion angle is part of the problem. Put GOOD shocks on the rear. The best double adjustables you can afford. By repairing the rear and partially addressing the suspension you're asking to throw good money away IMO. As far as differentials for teh street... There's only one I use. The Detroit Tru Trac. You should not ever run a spool on the street. Some guys do with success, I never will condone it. First and foremost its the cheap *** way out of getting the one up side of the limited slip. However it also stresses the axles (which is why aftermarket ones are mandatory in all racing bodies) and should it or an axle break, regardless of full throttle or part throttle, the car will make an immediate turn in the direction of the broken axle. So take a sweeping highway on ramp where you get on the throttle in 2nd, just as you upshift to 3rd the end shears off the axle in the inside of the curve... And you and the car go abruptly off the road. Not for me, an not in any car I build/work on. I'd prefer you not even be in the road with me, it is that dangerous.
You don't need a dana. What I see is you need a good rear suspension and you're worried about tossing good money away but leaving part of the problem in place. Shocks are a recurring problem on A bodies. It's a cheap and easy fix. MP had shock extenders in the 60s so this is nothing special to your car.
