Ooooo, bad idea. The 4g63 will not produce the kind of torque needed to push around the heavy ass GTO remember HP and Torque are two different things. Even with the turbo it would suck. It would be slow and lethargic and an all around disapointment. You are better off going with a smaller displacement car all together. I do not know what you budget is, but why not get the EVO or an older Eclipse GSX or Talon TSI. Good strong inline fours with the all wheel drive and all.