Hy mikedean58, welcome, your serial number breaks down as, W = six wheeler, 553 = 158" wheelbase, X = 1956 production I believe the balance of the number is regular production number which probably started at 1001. Your truck left the factory with a 324 cu. in. Oldsmobile V8 the standard equipment was an 11" dual disc clutch, an FO90 front axle, rear axles Eaton SS(A) 34M, transmission 5 speed 541GDS3. possible auxiliary transmissions 6231A or 6231B and air brakes, hope that helps
