Rolls Royce did in fact produce gas versions of B range engine, for civilian applications. I was once shown the ledger with entries for each engine and what they were used in, many diverse uses, sometimes standby generators, buses, Shell fuel tankers, even used in Bedford TK lorries operated by Marks & Spencer. There were comments in the book about overheating problems though, although this could have been due to other reasons, like inadequate radiator capacity, etc.