We can assume that the narrator is not actually Don McLean, because it’s not exactly an autobiographical theme. So it’s irrelevant what he actually drove.
His character, however, was a teenager who had a Chevy pickup truck. Based on the age of the character, I assume he owned a used truck. Judging by the era, however, I also would assume that he already had a fairly well-paying job and his truck wouldn’t be TOO old. As “The Day The Music Died” was February 3rd, 1959, I’m guessing that his truck came from the early ‘50s.
So, I’m going to pin it as a 1947-53 Advance Design pickup. The next generation is totally possible, too, though... I just get the feeling that his character is more rural, however, and might be turned off from the fancy new power steering and wrap-around windshield.
Are there any other cues in the lyrics that point to an older or newer truck? Is this not a big mystery and there’s already an official, ‘canonical’ car? I don’t know and I don’t care. This is what I’m going to picture every time I hear that song.