I had it on a 1981 C-20 454 TH400 4.11 gears. This was on a truck I had in Texas. Dual tanks, 40 gallons regular gas and a big LP tank in back that made the bed shorter than a 6 ft. usable space. 8 mpg with the gas and 3.5 on the LP. In Texas they taxed based on miles trucks were driven with a minimum of 20K miles. The Tag you had to get in order to fill up was about $500 if I remember because you just payed the sales tax not the Fed or state gas tax so after that it was not cost effective when I drove the truck only about 5K a year. I just remember how sluggish it felt when it was switched to LP. There was quite a bit of crap that made it work to switch off the fuel pump which actually bypassed and recirculated it back to the tank and special injectors under the base of the carb, the timing automatically switched and for some reason it would ice up on cold days and quit running. Switch it to gas and everything would be fine. It just didn't make sense to stay with LP. I just went to a Heat Pump with electric backup and got away from my LP furnace at the house. Yes LP is an alternative to fossil fuel just like E-85 but for now if you figure your operating cost per mile gas at $3 per gallon gass is still less even in an E-85 vehicle. My $.02