You need a better converter. I mentioned this in another thread not long ago. Find a converter company who "specializes" in what you are doing. There are a few that do very well with high RPM small block stuff. My choice would be A1 but that's just me. IMO you are likely needed a good deal more stall speed and something a good deal looser for sure.

"I am not ashamed to confess I am ignorant of what I do not know."

"It's never wrong to do the right thing"