stock tranny
#9
A rebuild with a shift kit and a good converter is all you need for 350hp. No need for really anything billet at that point. Are you gonna do the rebuild by yourself or have a shop do it? If you pull the trans yourself and take it somewhere to get a rebuild i bet itll be right around $1500. Or just upgrade the motor and wait for it to start slipping. It may not even slip or break at that hp.