1947 44 in gauge but I have one and seen others with 7U undercarraige making it 60 in
Engines will swap out between the D4 series machines from 4G thru 6U/7U series machines with some minor parts swapping, it happens a lot. There is a D4 7J or 2T with a LaPlante Choate dozer set up on it and a D315 engine on Ebay right now, the guy claims the dozer is a 1953 model year, the engine may be but the tractor isn't.