The side panel of the AMT '62 Corvair (and SMP '62 Valiant) Styline kits list the other kits in the series...at the bottom of the list is "El Camino". Presumably this would have been a third issue of the 1960 kit with Stylizing parts added (there was a straight reissue of the original version in 1961). Between production of promotional models, toy store frictions, and kits in '60 and '61, the El Camino tool was probably shot even at that point.
The Jo-Han 1969 kit "sell sheet" lists 1969 GTX and Cadillac convertibles, neither of which were produced. The 1969 Auto World catalog lists the GTX convertible also, not a Roadrunner convertible as I had previously posted.