Barry,
In concern of the core swapping issue... the few that we have done did not have a good success rate. We did 4, one chattered and one slipped, 2 we never heard back. Brandon's father was one of the people and his slipped. Boy, I would have never guessed, the clutch only had a few miles on it and looked good. We did our tweek and put the material on the disk and it still slipped. Must not have had the holding power that was needed. I then sent him a brand new setup and it worked great. The gentleman with the chatter was from Texas, we had some problems there and it ended up costing us a few dollars to try and give a deal. I don't know that the deal is worth the trouble.
Concering the clutch that started this post, this is a new thing that we're doing that is not even on our webpage yet but will be there by the end of the day.
We have had some center breakage with the clutch disk in the 5 speed and early 6 speed, non-ETH clutches. Heavy hauling coupled with heavy horse power coupled with 1 ton duallys (sometimes) and us making the clutch not slip could have a tendency of over torquing the center of the disk. So what we did to remedy this problem is, first, to realize in the 12 1/4" clutch it did not offer us enough room to put any bigger or stronger of a clutch center then we already had come up with, so what we are doing now is offering a clutch package where we redrill the flywheel to accept the ETH clutch which has a clutch disk center that is 3 times the size of anything that I could put with the 12 1/4" clutch. This also allows us to use more of the feramic material that enables the higher horse power so, in a sense, the OFE (organic & feramic up to 400 hp) or the FE (which is not available in the 5 speed) can handle, like CUMINNTSTRKN stated above, over 600 hp. This is a little more expensive way to go but assures no problems with center breakage.
If you have any questions on this feel free to call me and maybe I can explain it a little better over the phone. 1-800-988-4345.
Peter