[Caddylackn]

Propane is a great fuel to use, its cleaner burning and cheaper if bought in bulk. A propane only fuel system is good, but the gas/propane set ups not so much. To take advantage of propane you need to bump up the compression ratio to 11 to 12+ to one to take advantage of the higher octane (slower burning) of propane and also run more timing and a different timing curve on the distributor. There is 30% less amount of energy in propane than gas, so you need to take advantage of the higher compression ratio to make a propane system close to equivalent to gasoline in power and mpg. If you are at a stock 8.5 to 1 CR, the propane will make about 20 - 30% less power than gasoline. So there is no real reason to run propane on a stock V-8 unless its a fleet vehicle with really cheap propane available.

A truck setup that runs well on one fuel will run poor on the other fuel, so there are a lot of compromises made in compression ratio and timing. A dual fuel system makes sense if you are running higher CR on iron heads and don't want detonation. The propane can be run on hills and during towing and the gasoline can be used for starting and cruising. A propane fueled motor runs much cooler since it soaks up all the heat in the intake to vaporize the fuel. I have heard that it is very difficult to start vehicles in the winter on propane, so they start the truck on gas, then switch over when its running.