I put the clutch style unit in the last race of last year when I switched to 3.91 gears. It replaced the 4.11 cone type hog head I had been running the entire summer.
The 4.11 cone type is back in the car as of last night. Hopefully it will hold together until I can get something more permanent going.
At only 420hp your cone should last a long time unless its bad to begin with, is it burnt and only one wheel getting most of the power? if you want a clutch type look for a oem unit and rebuild it