Converting to propane is not worth the hassle anymore. Propane prices have gone up faster than gasoline prices. At one time propane was little more than half the price of gasoline, but after gasoline prices started skyrocketing in late 2001, the energy companies did not want a wholesale propane retrofit movement to begin, so they jack up the price of propane to about almost as much as gasoline.
Right now propane is only about 10 cents a gallon cheaper than gasoline. It would take decades of driving to get your Return on Investment (ROI) anymore. There is about a 20% horsepower loss with running propane as compared to gasoline. You can make up for that 20% loss by increasing compression, and installing a camshaft with lots of duration. Since propane is a high-octane fuel, it likes high compression. You can also get special camshafts for propane engines as well because propane likes lots of valve timing overlap.
