Two wire tenders for 31X PRR Pacifics came with 1946 and 1947 engines. They do not have a reverse unit in them. The 316 engine is a 5 wire design. Any tender with a reverse unit in it will work but if it is not originally from a 316 the tender wiring will need to be modified. The 316 needs 5 wires from the tender to the engine to run. It does not matter if the whistle is present in the tender or not.