If the Super Cobra is worth 5mil what is the Flip Top worth?

[Cal Metal]

I suspect that the reason for so few is that the processes for working with aluminum were still in their infancy circa the early 60s. General Motors, who had more technology than any corporation on the face of the earth back then, had some success in using it in the 215 cid Buick blocks. The Corvette, on the otherhand, discontinued the aluminum head option after 1960, having had a run of two years with marginal success. Cracking was the big problem, and the option was discontinued and did not resurface until 1967 with the 427 "rat motor" L79, an absence of 7 years. And then there was the infamous Vega.................