I have just built a super charged 5.0 liter for my mustang I took the 5 speed out of it and decided to go with a auto I installed a TCI stall that just came back from rebuild and its not stalling so I removed and sent it back and baught a brand new one I'm having the same problem with it. I was told that the pump in the trans might not be putting out enough pressure to make it stall. could this be my problem. I went back and checked for air bubbles in my lines going to trans cooler and back and it seems to have pretty good pressure I received my other stall from TCI and they said my old stall was tight and they had to loosen it up.  

If I were you I would give Harold a call at Dynamic Racing Transmissions. He's forgot more about the C-4 then TCI will ever know. Their number is 203-315-0138.
This is what all the fast NMRA racers go for trannies and converters.