Inliners International Forums General Discussion Engines GMC SBC valve swap

I have one 270 and two 302 GMC heads and none of them have a removable seat and none are shimmed. 0.21" is a pretty thick shim. But then I doubt any of them are in their original as built condition either.

I just checked the 47-54 GMC Maintenance Manual. The valve train illustration does not show a valve pocket locator or shims like the Stovebolt uses.