Thanks for the suggestion re limited slip diff. Just to share with you my idea of how this car will now be pampered. NO WAY is it going out in inclement weather after all this work. I have a newer 'technomobile' with fuel injection, AW tires, and modern conveniences for that. BTW here's an old timers story for you.
I remember the time, many years ago, driving this car in a huge, blowing snow storm. Made the trip home okay but the drivway was slighty up hill but the big deal was a drift as high as the hood at the end of the drive. Thanks to a neighbor struggling up the street in his car, I had to stop IN the drift. No problemo, no 'rocking', just ease into the gas and 4800 # of car (60% on the front) and just enough torque and I powered into the drive and garage with no slip no strain. FWD is really a good thing. So are good tires.
For my plans of use, a desire to keep the car orginal to the build specs, and prior experience, I think I'll pass on the 'posi'. Anyway, I haven't researched if there is such a thing for this slightly unique dual plantary diff.
My son put posi into his 96 Gran Prix. Along with a "couple" other mods and he's turning 12.6 sec. ET's. Again, no bad for FWD.