not sure on the 55-57 trucks, but on the 58-59 trucks the radiator stays in the same place for a 6 and v8.
the v8 has a fan spacer and a long fan shroud, the fan is ~4'' away from the radiator.
the v8 fan shroud looks like 8'' cut off the bottom of an oil drum.
i suspect the 55-57 is the same.
found some pics of my 59 panel with factory v8
