I own both an international "modified". irrigation propane engine in 304 and 392 size. they both read V 304 LPG and V 392 LPG where Howard described. I am assuming a factory modified 345 on propane would also read LPG there. I always assumed the factory LPG engines had harder valve seats also, being propane or natural gas was a dry fuel and the gasoline versions were made back when we had lead in the gas.