We used 1700 vw engines to drive our tanker pumps when decanting co2,we ran them on lpg.you will need various little extras,and the engine will normally run hotter on lpg.On our motors the lpg was gassed using a second stage converter ,part of which was a tube inside the exhaust silencer box.We always had to check the box before startup,if there was a frost line showing we did,nt start it,because it could have exploded.I should imagine the newer systems have cured these early teething problems.Personally i would leave well alone,lpg refuelling is not widespread,and many country garages are now closing because of the supermarket outlets being cheaper.lpg is also a very dirty gas,and leaves a deposit of grey slime in the carburation system,or at least ,it used to do.