These heads are a direct replacement for your tired and cracked 6.0l heads. New casting, brand new valves, seals and springs. So if you are going cab up why not go back with new instead of old questionable junk. These heads include machined O-Ring. The O-Ring is designed to keep the compression in the cylinder not in your cooling system.
No Core required.
Heads are guaranteed for 1 year from the date of purchase.