Also agree with Banshee.
Unless you know what your doing, or know someone who does, dont go grinding on the heads.
Just clean the imperfections and casting flash.
Seen many sets of clean valuable heads ruined.

I use longer valves-n-springs instead of machining the pads since the old vlvs usually need replacing.
Springs are a "throw away" item.
Thier junk compared to whats availible now.

Compression ratio vs tadays gas...thats a topic for anther day.
My cars run on regular unleaded.
But if had Banshee's $$$$$$ salery...