A friend of mine bought a 428 LPG engine short block from another friend that came out of a school bus if I remember correctly. I'm guessing the bus motor maybe had some kind of FT engine top end, like a 391, and that's why we only got the short block, but it had a 428 bore, crank, pistons, etc. This was many years ago. My friend then bought a set of 428 CJ heads from me and still has that motor. But I don't know anything about the LPG conversion. The engines run cleaner than gas engines. We do have some trucks and buses running around here in the U.S. on LPG and occasionally I read about a race car on LPG.