for starters here in germany propane or LPG is only 61 euro cents a liter versues 91 octane at 1.95 euro a liter which works out to be about 1.50 USD for propane and about 3.00 USD for 91. And remember thats liters not gallons. There is a little bit more mileage per gallon little more horse but in the end I am doing it for the cost effectiveness.
It also reduces tail pipe emissions by a pretty significant amount which helps the environment. I just watched a show recently (can't remember the name) where they built basically a one-off custom Camaro that was running I believe a big block 440 that was converted to run on propane. It made more power than a comparable gas engine and had almost no harmful emissions as well.
It shouldn't be too difficult to convert as there are a lot of places out here making conversion kits that people are using on Honda vehicles if you can't find anything locally to you. Converting to propane is actually one of the tricks people use out here in CA to bypass emissions inspections for cars with engine swaps that aren't legal otherwise. You basically get an exemption from testing from what I understand once you go that route. As far as cost though I really don't have any idea yet..
If you end up doing this make a post about it.. I've been interested in experimenting with propane for awhile, but haven't had an extra car or cash to mess around with it yet.
by the way, at this link it said the kit does not work on fuel injection... to the german (or temporarily german) thread starter, the more research you do the better. even the link i sent you had a tiny fuel rail... but i am sure that any company selling a kit would welcome a phone call and answer more specific questions for your car. i am happy for you...