LucaWRX: No, it came from a 1989 XT Turbo...
As somewhat of an update, I removed this diff to test with a welded "spool". I encountered the same wheelspin, further proving that I must be unloading the front inside by enough to overpower the helical LSD. I have made changes to the front suspension geometry and chassis stiffness to eliminate flex and lift "in theory". To be tested as soon as the motor is back together.
Changing these ramp angles is certainly on the list of things to do. I will update when complete.