You run on the east coast, so examples may not help, but if you are familiar with Sonoma, 2, 4, 5, 7/7a, 10, 11 are all problem areas. If you know Buttonwillow, the car will light up the right rear at 80+ going around Riverside (and most other power-on right handers).
A generous estimate would be 200-ish on both scales. Possibly less; it's a fairly well-used M52b28.
Bernal dad?
I don't know Sonoma but did get to run it once in 2011. yeah...you've got a lot of flat right hand corners that aren't really high speed corners. You want to be able to mash the gas and not think too much.
I use a dana powrlok in my autocross car, but it's not known to be a robust diff. I'm not sure I'd want to run one in lemons. If I used a clutch diff, I'd want to add a diff cooler too. Track down some bimmer guys and see what works for them...I've never studied the homemade diff coolers up close. The issue with the powrlok diffs (besides being uncommon) is the cross shafts break. The side gears are small, too. When the cross shaft(s) break, the gears get chewed up. Here are pics of a broken one I bought just for the '87+ case with tone ring.
http://www.pbase.com/towerymt/1030&page=all
In lemons...
We tried a modified G80 from a 940. I cut down the fly weight so it would engage above 20mph. What we didn't do was weld the weight/rod in place, so it must have flung apart somehow and got consumed inside the diff. Only symptom was 1-wheel-drive (obvious change during a race) and it dinged up the ring & pinion. Replaced the axle with...
...a welded diff. I was against it in principle, but I didn't have a better option for a reasonable price. 2-wheel-drive ALL the time with the welded. Pushes a little in steady state, can be especially noticeable in flat/off camber corners. But it makes the car easy to drive for every skill level. We were probably making 200whp at most and with 225s on 9.5", the rear always hooked.
We were using 700lb front springs at one point, but then dropped back to 475lb. I'd aim for somewhere in between. IPD lowering springs are way too soft.
We had revalved bilstein inserts that I had previously had valved for the 475s on my autocross car (as I upgraded the autocross car, the take-offs went on the lemons car). They were just adequate on road courses since they're mostly smooth. I believe the valving was 220/110 on the struts. More specs here:
http://www.240turbo.com/specsheet245.html#bilsteins
We had cut wagon overload springs on the rear, so probably not more than ~150lb. R-sport stiff rear shocks (p/n552198, 400/100nm), 25mm front bar, no rear bar. All poly rear bushings, but with the welded diff it doesn't really matter if you hike a wheel a little. Worst case, it can help the car rotate.
The game changer on the front end is the ball joint spacers that moves the bottom of the control arm out about 1-1.5" and got us about -3 to -3.5 deg camber.
http://www.pbase.com/towerymt/image/160231674.jpg
http://www.pbase.com/towerymt/image/160231672.jpg
Triple the front spring rate, confirm (or get) -3 deg camber at least, raise the front an inch, try lowering the rear if you can, and then play with panhard rod mounts & height.