Pre war and post war frames are the same, 2755-17. The steps are an added detail and can be added to any of these cars if desired. Likewise the warning placards. The 2855s had 4 placards. The 2555 and 6555 only had two but the other two can be added. Any sheet metal tank can be converted to any other with the addition or subtraction of these details including trucks and paint and decals appropriate for that car.
As for the flying shoe trucks, I will defer to the experts but believe the '45 set came with whirly wheels. The later flying shoe trucks came sans whirly wheels but with thicker axles.
Pete
