To look at an iron 300/340 head,(port sizes), it appears superior to all other oem heads. Looks can be deceiving ! Go on to the "Stan Weis" webbsite for flowbench reports, are revealing. For a hot street Rover, the ported/large valve, 64' head is still the best bargain,depending on the deal you swing for all the upgrades. Your results may vary. Good Luck, roverman.