they were installed for commercial use in cab overs and no they were not a big hit, just a big hit in the wallet at the pump 4MPG gas, some conversions were made to run on propane. but coming in a lil under 300 HP and 600 TQ it was a beast! and that was off idle 600 TQ! alot of people said they were two engines welded together but were actually one molded cast. there is a diesel version but its ultra rare since GMC went to the 6v & 8v Detroit within i think was 2 years of running these giant gas guzzlers. the MPG was the reason they only made them a couple of years but guys are finding them and firing them up after years of sitting which is pretty remarkable.