Hi Pilkie
I'd say the chances of finding one of these 2nd hand is very small - they are too desirable in themselves and when fitted to a vehicle it tends to make people hang on to the vehicle instead of scrapping it! Still you could try setting up a search in Ebay, try "LPG, V8" across the whole of the motoring section.
When I did that search it yielded RPi V8 LPG Kit You wouldn't be able to get a 120ltr tank in - mine are very full with a 65ltr - so that would make it a bit cheaper - but note you also need an ignition module to retard the ignition (by 7 degrees) when you are on gas - which would make it a bit more expensive. So the price quoted is probably pretty close to reality. Don't forget you might spend a bit of time and effort sorting out somewhere to mount the filler. I've got a dummy filler on the offside in the rear decker so that it looks like it's got twin tanks, a la Jag; but that was a pretty involved mod needing significant work to the base unit as well as the decker.
Hope that helps.
Chris
Edited By chrisyork on 1212860578