I have read that the PI engines have a deeper piston to keep the same compression ratio as before since the heads were lowered. So if you just put PI heads on a non-PI engine, wouldn't it increase your compression since the non-PI engines had a shallower piston dish and give you more power than a stock PI engine? Also would it effect what gas you need to use? The last question could be answered by Ted'98 since he has done this converstion on his truck.