It would really depend on how the rest of your engine is built, as to which head you would want to use. With no CC rule, i would be going with a milled 14cc head and get the piston up in the hole as close to deck as you possibly can, for max compression, but it really depends on the details of your engine. Post what you have in/on the engine and some can help you out a little better. Cam, Carb, Internal mods, external mods, timing, everything.