Hy bikeman77, welcome if I'm reading my parts book correctly, the V8 F350 series in 1957 (T) came with a Timken double reduction two speed. Check on the back of the glove box door there might be a data plate there which lists what the truck was originally equipped with. There will be a few choices for a replacement rear axle. Is the rear axle housing flattened on the top and bottom of the housing, or is it round? If you could post the serial number it might help us to identify which components were on the truck when it left the factory. Hope that helps.