Tom,

As you most likely know, the GMC Fleet Option trucks were a specific option available from GMC. They came with different exterior body parts and interior colors/parts than non-Fleet-Option GMCs. Here is some information about 1955-1959 GMC Fleet Option Trucks.

You might want to join OldGMCtrucks.com discussion board. Some people over there might have GMC Truck Data Books with information that might answer your question(s).

Tim