There are a few guys around here who have swapped 4v's into their GT's. It will bolt right in...its an easy swap. Do you mean a Cobra block complete with pistons, rods, crank etc...? The Cobra crank is stronger than the GT's, I believe it can handle anywhere up to around 700hp if I remember correctly...I'm not talking about pistons and rods holding up to that amount of hp....but the crank should get the job done.