MODEL YEAR: To the right of the “ST” letters (short for “Style”) are the last 2 digits of the model year of the car. “64”=1964, “70”=1970, etc.

DIVISION SERIES: The first digit of this code identifies the GM division (1=Chevrolet, 2=Pontiac, 3=Oldsmobile, 4=Buick), the second and third digits identify the series (Chevelle, LeMans, Cutlass, Skylark, etc.). While the series code on the data plate may not match the series code in the V.I.N., it must be from the same family (the series code will not represent an Impala on a Chevelle data plate, or a Catalina on a LeMans plate, and so on).

decoding 1964 Chevelle options

Division Series:
53- Chevelle 300 or El Camino, 6 cylinder
154 – Chevelle 300 or El Camino, V8
155 – Malibu or Custom El Camino, 6 cylinder
156 – Malibu or Custom El Camino, V8
157 – Malibu SS, 6 cylinder
158 – Malibu SS, V8

Body Style:
11- 2 door sedan
15- 2 door wagon, 2 seats
35- 4 door wagon, 2 seats
37- 2 door sport coupe
45- 4 door wagon, 3 seats
67- 2 door convertible
69- 4 door sedan
80- 2 door sedan pickup

Assembly Plants

A- Atlanta
B- Baltimore
H- Fremont
K- Kansas City/Leeds
L- Los Angeles/Van Nuys
1- Oshawa, Canada
2- St. Therese, Canada

Source:
Standard Catalog Chevelle 1964 – 1987 by John Gunnell