Even if you had a set of X heads on the bench that needed a total rehab, the costs to rebuild and up grade is more than a set of current full loaded aluminum.
Most current aftermarket heads come with new 2.02/1.60 valves that have smaller stems and the seat is fresh. New bronze guides. Springs for over 0.600" lift. Raised ports. Smaller CC chambers in a swirl shape. Huge port flow before porting.
