Stock diff with truetrac and solid spacer will hold around 450 wheel ft-lb. (you will need a stronger trans and driveshaft, and a larger input flange on the diff from the 7.5" front of an old pickup or 4runner). And that is if you have the traction to put that much to the wheels. If you have a good ECM that can limit the boost pressure in the first gear or two that will help a lot, and will probably be necessary to maintain traction.
Above that, you will need to replace the diff and axle shafts. I am working on integrating a GX71/MZ12 8" diff that has mk3 internals but similar mounting to a mk2 diff. Will need custom axle shafts of course as it has 6 bolt stubs, and they would be the next point of failure anyways.
Using a T2 Torsen with a torque bias ratio is around 2.5:1 so you can only ever get about 71% of the torque to one wheel, and 3.73 or 3.90 rear gears, I wouldn't be as worried about the stub shafts in the control arms so much. I've only ever seen them get broken with welded diffs and low gearing (4.30 or similar). The splines are pretty big.
I have found that the 450 to 475 WHP range (550 crank or so) is the functional limit of the mk2 chassis if you still want a car that is reasonable on the street or track. Above that it is either a poor drag car or just makes lots of tire smoke.