Pro Design Cool Heads are an excellent product, but still need to have the squish cut correctly. The can also be modified to run O- ring gaskets, doing away with the normal head gasket. This requires some machining and welding of the water jackets above the exhaust port. They can also be fitted with a decompression button for you guys that aren't man enough to kickstart a zilla or want a 250/500 thats easier kick for your Wife/GF or kids.