It can be done :
http://www.sbautogas.co.uk/recent_conversions/pictures/Bedford%20Bambi/bedford_rascal.htmI'm looking to buy a cheap system that is compatible, however the problem is working out what tank to use. They come in various sizes and flavours, donut shaped and cylinder shaped as seen in the picture. One place a donut tank could go is under the spare wheel, just possibly. Otherwise the cylinder under the bunk seems to work fine.
I can't see the price of petrol going down below 130 for any sustained period of time. Too many greedy commodity traders and oil companies will hold stocks to keep prices artifically high. Then throw in 'peak oil theory'.
LPG is the only way to go in the long run.