My 50 canopy express (1/2 ton) has plank floor. Again - it is odd that yours is plywood. I have seen a plywood floor in a 49 canopy express clone that was made from a suburban. The newest CE I have seen is a '54 GMC 1/2 ton which also had a plank floor.
Does anyone know of factory literature on these which might show if it was an option?
Ken