Sorry just skimmed the rules, then how 'bout this.
That's exactly what I was going to say, the Corvair. It was indeed brilliant - a rear-engine, air-cooled car built in Detroit (and California, and St. Louis, and Canada, etc.). But even though it was offered for a full decade (Oct 2, 1959 to May 14, 1969) and in a range of models, sales weren't exactly great.
1960 Corvair 700 sedan:
1961-1964 Rampside pickup:
1961-1965 Greenbrier van:
1961-1964 Corvan 95 (seen here with the desirable 8-door option):
1961-1962 Lakewood wagon:
1962-1964 Spyder (also available in coupe form):
And there were special offerings from the aftermarket, such as John Fitch's Fitch Sprint:
And if you wanted to go racing, you called up Don Yenko and ordered a Yenko Stinger in one of four tuning stages:
And of course the 1965-1969 500/Mona/Corsa coupes and convertibles:
And yet, after all that, it was considered a "failure". The Rodney Dangerfield of classic cars. And the birth of Ralph Nader's career... whatever he does.