Swirl-polished oversize Stainless valves are available in full sets of (16) for all heads, 1968 through 1979. They are ready to install with 11/32” stems, and any competent machine shop in your area can machine the oversize seats. We do not recommend installing false hardened seats unless you are repairing a damaged head, nor do we recommend reusing stock valves. With the high nickel content of the Caddy heads, and stainless valves (which are very difficult to damage), you should be able to get many, many miles of trouble free operation from your upgraded heads, even on unleaded fuels.