I have done the conversion on several vehicles over the years. Been running diesel now since 1990 since my last LP truck.
Been seriously considering going back to LP gas on a new F-450 I'm getting ready to order.
I still have most of the peices to convert and all mine have been dual fuel and you keep the original carb and should switch to gasoline at least once a week to keep the carb in good shape.
You send liquid to the engine and a vaporizer converts it to gas to be burned in the engine.

Oh wait, I do have a 4 cly forktruck now that runs on LP gas that I converted from gasoline about 10 years ago. I have had chev trucks, ford trucks and a caprice car that have run on it.
It is gonna become more popular again if gas prices stay high.