When Does "One Piece at a Time" (1976) Take Place?

"One Piece at a Time" is a comedy narrative song written by Wayne Kemp that released March 1976. So when is "One Piece at a Time" set? 

It takes place roughly in the year: 

~1979 AD 

We know this because the voice of the song gives 1973 AD as the most recent automobile part mentioned in the line "And the motor turned out to a ‘73"... It is not entirely clear if that is the most recent part available but it therefore must take place after 1973 AD. 

More specifically, we are led to believe the song covers the main character's entire Cadillac car (bought by General Motors in 1909 AD) factory career from 1949 AD to 1979 AD because of the early part that goes "But I figured I'd have it all by the time I retired" and the International Union, United Automobile, Aerospace and Agricultural Implement Workers of America a.k.a. the United Auto Workers union successfully struck and won a retirement plan with 30-year pension from the Ford Motor Company in September of 1949 AD in the real world. GM followed with a similar 30-year plan in 1950 AD. So a Cadillac factory worker who started in 1949 AD would be up for retirement in 1979 AD. 

1949 + 30 = 1979. 

The first half of the song is essentially a flashback explaining the unnamed character’s process. Only the beginning is clearly marked by the opening three lines: "Well, I left Kentucky back in '49 / And went to Detroit workin' on assembly line. / The first year, they had me puttin' wheels on Cadillacs." as being in 1949 AD. This is also when the scheme first begins since when asked at the end of the story, "Uh, what model is it?", they answer, "Well, it's a '49, '50, '51"... meaning that the earliest-model parts are from the very first year this person worked at the Cadillac factory: 1949 AD.