Propane units are $3500.00 installed.
A quick video on how a conversion to LPG is done
DUAL FUEL UNLEADED PROPANE
Now you can run your vehicle on propane instead of unleaded fuel all the time. Propane is much less per gallon than unleaded. The savings can be as much as half the cost of fuel your currently buying. Here in Washington we find our local LPG distributors to be on the average of 45% less for propane over the cheapest unleaded.
The system comes complete with every thing you'll need to drive every day on propane. Tanks, mount for the tanks, fuel lines, Propane throttle body injection (TBI) and mounting bracket, Automatic safety venting valve, Thru hull fitting, all fittings to connect components, coolant hose to connect fuel vaporizer, Fuel vaporizer, Vacuum 12 volt switch for TBI, 12 volt switch for propane, toggle switch for dash, sealant to make air cleaner intake attachment point for the TBI and misc. fittings to make it all come together.
Expect a slight decrease in fuel economy running on LPG as it has just a little less BTU's per gallon as Unleaded (10%). Lets say you get 45mpg now. On propane you would get 40.5 mpg. If your paying half the price for propane the money savings would be equal in this equation to 81mpg over your current unleaded. Our if you were paying 25% less for propane it would be equivalent to 50.6 MPG.
With this system at any time you can run on either unleaded or propane at the flip of a switch. The car is unaltered for the most part besides mounting a switch on the dash and a thru hull fitting in the spare tire hole. This system can easily be moved from Geo to Geo if some one chose to.
The real key to this system is the Vaporizer and the propane TBI have been custom built and dyno'd for your specific engine. The system operates in subzero to very hot environments. Some where in the cold range of the scale you may need to start the car on unleaded and bring the propane up to temperature so that it can vaporize the needed volume of fuel to drive on. Propane evaporates at -45f so it doesn't take much heat to get it up and running on propane. The engine coolant from the unleaded virtually has it handled as soon as it holds any warmth at all. So from the hottest desert to the coldest pole you can keep on driving your Geo Metro.