Sven,
Your truck IS a 1958 as confirmed by the serial number and the hood & fender emblems.
The frame numbers never have the "series" number/letters stamped that the door post tag would have.
Here's the way your serial number 58K104306 breaks down. You door tag should start with 6B.
6 = 60 Series
B = 156" wheel base
58 = year
K = Kansas City Plant
104306 = unit number out of plant K starting with 10001
ALL parts in and on the Cab are the same as the pickup trucks, as are the inner fenders and hood. The fenders and grille are shared with the 1958/59 Series 40 trucks.
Mike B
