Different styles of front hood bumpers used from 64.5-69 (maybe later also?)
Starting on left, this is the first style, most common on 64.5 cars. Middle one was introduced sometime during '65 production and ended around April '65. The one on the right is the most common, being used from about May '65 all the way through the end of '69 production and possibly later. Would be good to narrow down the production use at the 3 assembly plants. Here's a start:
Flat top open screw:
Dearborn - March '64 - September '64?
San Jose - July '64 - ?
Round top open screw:
Dearborn - Start? - April '65 ?
San Jose - Start? - April '65 ?
Metuchen - Start? - April '65 ?
Round top, closed:
Dearborn - April or May '65 - August '69 ?
San Jose - April or May '65 - August '69 ?
Metuchen - April or May '65 - August '69 ?