[wbkinsey]

The assembly plant code is the LETTER directly following the year designator, in your case 58. Here is a list of the code letters and corresponding assembly plants.

'53-'64 Factory Codes
A Atlanta, GA
B Baltimore, MD
F Flint, MI
G Framingham, MA
H Fremont, CA
J Janesville, WI
K Kansas City, MO
L Los Angeles, CA
N Norwood, OH
O Oakland, CA
P Pontiac, MI
S St. Louis, MO
T Tarrytown, NY
V Southgate, CA
W Willow Run, MI
Y Wilmington, DE
The code changed significantly in 1953. VINs now had: Series (single letter); Model Year (last digit of the year); Factory Code (now changed to letters); and Production Order symbols. Each series was separately numbered in sequence for that particular plant (Starting at 001001).

Example -- L54A001901

Series Model Year Factory Code Production Order
L 54 A 0001901

The truck in the example is the 900th 1954 1-Ton truck built at Atlanta.





1955 2nd Series (First of the "Task Force" trucks)

With the '55 2nd series came some more changes. The first symbol was the code for the Series of the truck (1/2-ton, 3/4-ton etc.) and the second symbol was a "2" for second series of '55 trucks. The 3rd and 4th symbols were the year, and then came the plant symbol. Last of course, was the sequence number (6 digits and started with 001001 at each plant).

Example -- H255J000101

Series Series Model Year Factory Code Production Order
H 2 55 J 001101

The truck in the example is the 100th 1955 Second Series 1/2-Ton truck built at Janesville.



1956 - 1959 ("Task Force" trucks)

The first and second symbols indicated the Series (all light trucks had a "3" in the first position). Third and fourth symbols indicated the two-digit year. The fifth symbol indicated the assembly plant (now changed to letters from numbers). Last was the the sequence number (6 digits and started with 001001 at each plant).

Example -- 3G56F001001

Series Model Year Factory Code Production Order
3G 56 F 001001

The truck in the example is the first 1956 1-Ton truck built at Flint.

Hope this helps.
Bruce