With all that said, the compression ratio has to be brought down if you want to use pump gas. You really need to measure everything, meaning piston to deck height, head gasket cc, along with the 67cc chamber assuming that is correct. Plus any specs on the pistons, compression height and dome displacement. The true measured comp ratio is needed to pick your final cam choice as it will dictate the dynamic comp ratio and the ability to run on pump gas.
Your goal is definitely achievable, just got to get all the ducks in a row. :thumleft: