I did find one site on the net that lists the differences here -
http://www.camarotech.com/steering.html
But, here's the basic run-down. GM steering box P/N 7839897 (stamped WS) travels 35 degrees, and GM steering box P/N 7843512 (stamped HX) travels 32 degrees. So, if you have 16x8" or larger wheels, you really should run the HX box to avoid fenderwell issues.
The performance G-body box travels 39 degrees which is even worse, and why a lot of guys I know with huge wheels up front (like 9" wide) swap to the F-body box. It's not an issue on my car, since I only have 8" wide wheels, and the G-body fenderwell is huge compared to the F-body.
