ok guys i need some advice for what work should be done to my head, i have the 5k with 4age pistons, stage 5 cam, that was used in ke25racers car, i am going to use a 4k head off my old motor, but thats stock atm, i have a downdraught holley and extractors and was wondering how far to go with head work? would it be most reliable if i leave it stock?