Sears sold  hardwood box  versions of the 10.5 cubic foot riding and hauling cart, very few have survived.
Original featured Quick & Easy hitching - clamps on saddle and one pin on rear hitch hole  allowing  adjustable handle height, tension, flexibility and tracking.
DB riding sulky was equipped with 4.00x8 semi-pneumatic tires, bronze bearings on  7/8" axle and 'self energizing' friction  type brakes
By using  a 1-1/8" axle shaft you can use spare tractor hubs on your cart by removing the ratchet springs and pawls.