Cometics are MLS and require a specific finish on the block and heads. Mine does not have that finish and everyone I've talked to (Cometic and engine builders) say they won't work properly.
Lots of people run them with the "wrong" finish as is with no problems and some do it by spraying them with Coppercote or some other sealant. Cometic doesn't recommend this but I'm sure it's more from a product liability view than reality. They have no idea how "wrong" the finish that a customer has might be so to eliminate any leaking complaints that aren't their fault, they dictate the installation procedure.
Mopar used to run shim gaskets OEM and I don't recall any specific deck finish for those. That was a metal to metal seal as well.
Kevin
