... Now closed chamber heads for the 318 would aid compression and mixture motion. A person with some welding experience could build a furnace to heat a head to cherry red and weld up a quench pad into the chambers. Then it needs to be cooled slowly over a number of days.
Back in the 1940s to the 1960s, Chevy guys would do that to the 216 and 235 6 cylinder heads to raise compression as far as 12:1. Of course guides must be checked and possibly replaced after and then a complete valve job after grinding the combustion chambers to.conform to the new shape and volumn. Then the head surface needs to be milled for gasket seal.
I see minimal difficulty doing that to 318 heads to raise compression and gain mixture motion which prevents detonation. A little pocket porting and port matching with a carbide burr and you could have decent heads. Lots of time but minimal cash outlay involved.