there's lots to choose from now, turbo's have come along way. years ago it used to be, t34, t38, t4 but there's lots of choice now
most will depend on budget tho.
gt3071r seems a popular choice but the new gtx range seems the latest big thing
you can have a gtx3076 which apparently spools like a gt3071.
who's your tuner, what HP are you aiming for?