Hi, Obviously buy one already converted, and like the others say , lpg is under half the price of petrol . I also worked mine out to an equivalent 26-28 mpg. I bought my '92 se vogue last year , which had been converted in 2000 ! It has been totally reliable for the past year and when i had it safety tested two months ago , the examiner said it was well installed system , still using all the original fittings ! Its a LOVATTO system , with twin under sill tanks (60 ltrs.) The engine has done 160000 miles with oil changes done religiously through its life which included caravan towing throughout europe . The previous owner told me it only broke down on him twice in 8 years , both times on his drive !!
So , try to buy one with a full service history , not many owners , and as low a mileage as possible .That will sort engine /transmission reliability out. Now about the chassis and bodywork ..........!!!