I've a couple of engines I run on propane, as I use the gas for the burner on their hot tube ignition it makes sense to just tee off for fuel. Inlet valves incorporate a demand type regulator so gas only flows during the intake stroke.
Also have a couple on vapour tanks that just draw petrol vapour rather than the liquid so won't flood. these are spark ignition 4-stroke and a modified loyal cycle engines
I have a number of throttle governed multi-cylinder model engines operating on vapor propane. They all normally start in one or two spins of the flywheels, no cylinder carbon build up, will not flood, near odorless, and are in my opinion safer to operate at shows. And, propane is very economical now that legal refillable 1 lb bottles are available.
I use the smallest RC carbs I can find with the needle turned out a few more turns. The only other requirements are a demand regulator regulator (Jerry Howell best design), and a tank regulator (Weber Go Anywhere Grill). You can operate more than one engine off a single bottle and demand regulator. Fuel pressure needed is very low (4" water column).
Propane is little different and you can create problems for yourself if not ware of its minimal issues. Chemically propane combustion yields a little more water vapor in the exhaust gases than gasoline. If engines are run for short periods and do not get warmed up, you can get corrosion in the cylinders. This can be mitigated by running the engine longer until it warms up, and/or by always opening the throttle and spinning the engine a few times after stopping to purge any cylinder moisture. Short runs can also allow blowby gases to accumulate moisture in the cool crankcase oil which becomes evident by milky looking oil. This is a common problem in short use fork truck engines on propane that never get warmed up, not just model engines.
Once you get used to running on propane you probably won't go back to gasoline.
I have install propane carbs on engines. It just buying the propane carb Amazon about $20 to $40.00.
It takes 1 to 4 hours depending on location and engine. The last one I did about 2 years ago and it was a tri fuel carb gasoline, propane and natural gas. Cost $30.00.