Buy the $89 stock Hi-compression 340 pistons for sale here recently
[FOR SALE] - 1971 OE 340 PISTON SET
and run her on good gas or E85. That **** is 100-105 octane and should be available about anywhere soon. I had a 273-4 and it never knocked on crap CA gas to boot. If they over rated that compression ration, how honest was the 340's?