Already running low 12's on the motor with a 98 GT auto? What does he have done to the car already?

I'd probably go with an aftercooled Vortech unit. His car would still be street legal with most Vortech kits. He might want to look into a TDC (Turbo Driven Concepts) turbo kit for his car. It would be quiet and make tons of power. Just do a search for TDC's website on yahoo.