Gear ratios are different on the DI. Since the tires were usually smaller, the rear sprockets are too. My '51 DI is so heavy I wouldn't consider pulling with it without some serious modifications. The front axle, rear wheel brakes, radiator casting, etc. all look like someone forgot to stop pouring iron when they built it... gotta love Case! About the only thing lighter versus a normal D is the grille. There isn't a motor lift or a belt pulley and it has a foot clutch. Hope this helps.
Ken in AZ