Don't know where you live, but the state of Missouri has a extra propane license (in addition to the normal license plate fee) if you have propane on your vehicle WHETHER YOU USE IT OR NOT! This fee used to be an extra $110. per year, don't know what it is now. Additionally, expect to pay state and federal road taxes on the propane when you buy it. You cannot fill the propane tank on the vehicle without the propane license.

Also, propane has 91,000 BTU/gallon, as opposed to gasoline at 117,600 BTU/gallon. Your fuel economy will drop.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop