The October '06 issue of High Performance Pontiac has an article (Part 1) on this subject. The test car is a 4th-gen F-body.
This first installment mostly goes into teardown and parts inspection, but it does give what they call "Five Steps To A Stronger Rear":
1. Weld the axle tubes to the center section.
2. Use a T/A differential cover with bearing cap preload screws.
3. Replace the weak factory axles with aftermarket.
4. Replace the Torsen T-2 differential with an Eaton or Auburn if you are at or above 400 rwhp. For road racing or autocross, replace it with the heavier-duty T2-R.
5. Use a high-quality ring and pinion. GM makes some of the best.
They claim that steps 1-2-3 will strengthen the rearend by 20%.
Parts Sources:
Texas Drivetrain Performance, Fort Worth: www.texasdrivetrain.com
Randy's Ring and Pion, Everett, WA: www.ringpinion.com
Peyton Performance Automotive, Inc, Waxahachie, TX: www.peytonperformance.com
I found this interesting, if they are correct in their assumptions. Those of us here have always heard that the stock 7.5" can live with up to about 300 rwhp, but I had not heard a HP figure for the Torsen T-2. These are the same differentials you can buy from SLP Performance as "used take-offs". They are supposedly low-mileage units that they replace with the T2-R. Apparently, this article infers that the Auburn or Eaton are better for drag racing than the T-2, but the HD T2-R is tops for curves.