Re: I had a breakdown today...
KC, I recently bought a 6" 600grit diamond flat lap for another project for $17 including the freight... same same as a honing stone, almost. Any grit is available. rocklady1 on ebay.
In the past I had lapped mc cylinder heads using clover compound on a 12" square of thick glass. It worked fine. I guess the clover compound is just silicon carbide in a grease medium.
and CT, it's not really necessary to have a magnificent mirror finish on the mating surfaces... I've done many, and basically just look to see that they are 'frosty' in a uniform way all across the gasket bearing surface.