ARP or A1's work fine. 12mm is usually all the bigger you have to go. O-rings work well with that setup. I run fire rings on mine but I tear the head down once a year and go through it all so I don't have to worry about failure due to race or daily driving. Some will say a normal head gasket, some will say fire rings, others, o rings. With 55psi you getting at the max of a stock headgasket. Upgrading is usually around the corner.