Looking to convert a 410 merc that is currently running on propane to gas. The engine was built for propane, and I've no experience with what must be done.

The engine is in a 1970 Ford, so the wiring shouldn't be too hard to tackle. I'm not interested in tearing the engine down and swapping out the pistons, but uncertain what head work needs to be done to get the right compression ratio.

Any advice would be much appreciated.

Thanks!