Scouring wrecking yards over the last 35 to 40 some odd years, I've seen both "riveted" and "screwed on" AC Delco covers. I'm not sure why since (I believe), AC Delco was the sole supplier. I could see variances if there were more than one supplier, but I don't understand why the two versions from one source. Of course, one or the other (riveted or screwed on) could have been an "over the counter" replacement, so I'm not sure which one is correct. Riveted? Screwed on? John Hinckley, I'm sure this has been chewed up many times on the Corvette forums. What's the consensus?