Bill aeroflow make a 65 cc head for the 340 here you can get from Rocket Industries bare just have them gone through as they will need some tidying up. I am using them on my stroker. No issues just get them checked over as guides will need reaming , had mine cc came out to 64. All threads were good I just used my own gear to fit them out. For a decent performance set up they work well if you massage the ports and get them breathing to suit the cam your running. And to add get the B 3 kit for your geometry if your running rollers.