I assume you want to know costs. Most vehicles 1990 and older (trucks are the least hassle to convert) will run approx $2000- $3000 depending on the dealer. Newer vehicles 1990 and up add about $1000 to that for computor support. Word of warning I do not recommed converting high mileage engines unless a) your planning on a rebuild or b) it was rebuilt in the last 50000 miles.
The biggest cost item is the tank, but somtimes you can find a gently used one for less money.