Like an idiot, I didn`t address the spark plug application on my 292. The best I can figure is it takes a flat gasket 14 mm. 5/8 reach. I`m used to using the ngk because of the heat range options (non resister). I`m using an HEI which I have no experiance in. My head is 1968 vintage. Any suggestions? This motor is for bracket racing. THNKS
