There are not many differences between the '54 and '55.1, but there are a few.
For one, the '54 still used the enclosed drive shaft while the '55's had an open drive shaft.
The emblems on the sides of the hood were different from '54 to '55. Both had "3100", or other model, emblems, but the emblems on the '55 were larger and totally encompassed the "3100".
The second & third digits of the VIN plate, found between the door hinges on the drivers side of the cab, should be either X54XXXXXXX or X55....
There may be other differences, but these are the ones that I come to mind.
