I would think that March through June 1964 cars would ONLY have what is Pictured in Pic#1. and July 1964 and after would have what is pictured in Picture#2, Though the car could also have the Metal "Deluxe" style belts as well as in Pic#1 since after 7-64 both were offered at the same time. It depends on the early build date of the car.
The "Standard" Plastic Clamshell belts were not available before July 1964, The earliest date stamping I have found for the Plastic Clamshell "Standard" belts is "7-64". The Metal "Deluxe" style belts were offered first, and the ONLY belts available until July 1964, Then both the "Standard" Plastic Clamshell and "Deluxe" Metal ones were available. The "Standard" Plastic Clamshell belts were either ALL BLACK, or Color Coded to the Interior color, and the "Deluxe" Metal ones were either ALL Chrome Alligator skin Deluxe Buckles with Black or Color Coded belt material or Color coded Metal Deluxe Buckles with Buckles with Black or Color Coded belt material.
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Tony K.