I am going to go against what everyone else is saying.
how much do you want to spend. I built a propane kit for less than $200. It added so much fuel mileage that it doesn't cost anymore to run than running straight diesel. Also it adds more power than the turbo. I have had turboed trucks and non turboed trucks with propane. Propane adds more power. Now I have a truck with propane and a turbo. Real sweet.