I broke it pretty good. I thought the rear end held up good (Just chose a bad time to go). I have a 9 inch out of a 1958 F-100 with 4.11 gears (It needs rebuilt though). I would like to put a 3.89 gear in it, so I can keep about the same et because I plan to run a 14.0 index class next year.
Trust me, I am pushing that skinny peddle more than hard enough.
Just a little update. After I put the original rear end back in, I found out my tranny was also broken. Today I finally dropped the tranny. It had a slight burnt smell to the fluid. The fluid was contaminated with little metallic particles, but cleaner than I thought it should be. I also found out my converter is trash (It rattles when I shake it, like the complete inside came loose). I will hopefully take it apart this week or weekend to see what else broke. I hope not much more.