I've actually looked into Propane and Ethanol for the old bolt. One of the biggest drawbacks is that the "alternative fuels" are typically a "dryer" fuel than what gasoline is. What makes them a cleaner burning fuel is that they don't have all the impurity's and additives in them, so there is minimal upper cylinder lubrication. Running stainless valves and hardened seats is almost a must do.
Another drawback is that these engines don't have a high enough compression ratio to efficiently use any of the alternative fuels. The best you could probably hope for is about 8.5:1 compression with an old stovebolt without have custom pistons made. Propane likes things in the 10:1 or better range and Ethanol in the 11:1 or even 12:1 range.
You have to decide what you want and build your engine accordingly. Updating to a newer drivetrain may be something to consider also. I'm actually considering swapping a GM 4.2 in place of the old bolt and running alchohol. It has 10.5:1 compression right out of the gate. The stock Delphi injectors are already ethanol compatible. One of the biggest obsticles is the wiring, but the aftermarket is alredy taking care of that too.
All the parts are available in the aftermarket to do a conversion to whatever you want. From Viton gaskets to complete LP carbs. My opinion is go for it. Why stick with convention? Different is good.
Chris
