Does anyone have experience with compressed natural gas (propane?) conversions? A long while back I used to smog some Ford tow trucks that were gasoline/natural gas capable. Seems the engines didn't last as long due to cylinder wear but were always extremely clean when torn down for rebuilds, the power was down and mileage wasn't as good as gasoline. Newer EFI systems are not as adaptable to natural gas, but older carbed cars are fairly simple as I remember it.

57 Black Tbird 312/auto