To clarify a point.
You get a bit less miles to the propane gallon, than with gasoline, however, as mentioned, the savings are still very substantial, for the lower price per gallon.
You can expect approx a 60% savings.
I investigated the heck out of the conversion, as I wanted to convert my RockyMobile/Olsmobile 98 with it's gas guzzling V6.
As it turned out, there was a run on installations at the time, and I couldn't get a decent size tank, so the plans got delayed.
Along the way, I kept on asking questions and observing, and it is the general concensus that it damages your engine.
Apparently this would not be the case in other parts of the world, as the standards are higher for the equipment, but it is the case here.
If you want to know for sure, just go hang out at a busy propane gas station, listen to the exhaust coming out from the propane public cars coming in to fill up.
They sound like they are gurgling under water, a little like an inboard/outboard diesel engine on a boat.
The guys who run the station, if they are honest with you, will also tell you that it prematurely wears out car engines.
My other source of info was from Espaillat Motors, and being the good friends that they are, they highly recommended that I do not make the conversion, specially with an old engine, as it could have been the straw that broke the camel's back.