Gas, converted to propane, but that's all the customer can tell me. He's been told it's an International, but I don't think so. Distributor looks to be rear-mounted.
Actually without being able to lay eyes on it in person, it could be one of the smaller engines in the same family from IH, the 461 or the less likely 401 judging by the looks from this pic. Anyways, it is definitely IH.