That's even better with 3.73's, did you try a 4.11 gear? I thought you did? My mistake if not.
I'm thinking of putting the 3.91's in my stock diff untill I can get the HammerHead, I already got the axles installed, just have to change the stubs that go into the diff to use my axles. I was going to go with the ZL1 diff, but I wanted to piece it together.
I broke a axle at the line too, I even got a video (in car) of it I will post when I get home from work.
I love the twin disc Monster clutch, I'm hoping I can slip it a little better then the single. I leave the line at only 2500 RPM, due to stock tires & gears, my average is about a 2.3 without killing it, wheel hop is violent if any better, with the stock low profile tires!
I'm used to an auto at the track so this is a learning experience with me too, but you got a whole lot more POWER then me, I'll get there soon enough!
Here's the video link when I broke an axle-
Here's one spinning 1st-
Here's one of my stock decent runs-