I currently have a super phat shaft 66, what other turbo can i run with this to have twins?

 

Depends on how big your injectors are and how much fuel you are pushing. My guess is if you arent overfueling your 66, it is too big for a top turbo. If you have the fuel, i would go with the new borg warner ldp (low drive pressure) s480. But more realistically probably an s475 with a small a/r would suit you fine.