I did some research on using epoxy to fill in some eroded spots on the gasket surface of the head and exhaust manifolds on the Ford FE 390 I just rebuilt. I went with Devcon Steel Putty. It does not have the bonding strength that the more liquid epoxies have but does have the durability I was looking for.
Check out
Project Farm's video's on epoxies. He tests them with real world techniques and expectations.
I'm currently anti coolant sealers, I believe that they led to the cracking of my block due to the pressure relief in the radiator cap getting stuck shut. I may be right, I may be wrong. Your mileage may vary. In my case, it blew the lower hose off, cracked the thermostat housing, blew out a freeze plug and cracked the block.
Michael