I think you mean a C4. However i would say that the car would become useless for roundy round after changing it. Ive never heard of anyone ever anywhere using an automatic for oval racing. What i was told is they cant hold up under the severe stress that kind of racing puts on them. Sure a Drag race C4 trans will hold 1000hp for a good # of passes, but they get a chance to cool down and "rest".
 I could be way off base here but its what ive been told and heard.

Good luck with the car!

I drag race a 2.3 with a C-3 trans and it holds up just fine now. After some mods it will last just fine. The biggest thing was a good trans cooler with big lines to keep the fluid cool. Try to find a 1981 or newer it has better internal parts.

P.S. alot of short track guys are running automatics these days.