My all steel 440 Sixpack powered 4 speed Challenger broke it's stock axle the VERY first time I took it to the track with ET Street tires.
I tried to launch the car extremely hard when the axle broke.
I replaced the axles with Moser ones and have ran the car a few more time at the track since without breaking anything but I have been doing much easier launches. My car has run a best of 11.80. I will definitely have a Dana under the car before any super hard launches again.

I think an 8 3/4 could be built(modified) to survive behind a 500-600hp automatic car(no trans brake) but NOT behind a heavy, 4 speed, big block car with sticky tires running at the track on a regular basis

4645145-launch.jpg (90 downloads)