Reading up on Earl Muntz, I see that he made a ‘convertible’ sports car with an alumin(i)um body, a removable steel hard-top (couldn’t bring it with you), seat belts, other features. It may interest you motorheads. Apparently, unlike his Motor Mansions, there are a few around still.
Nothing unique there. Pierce Arrow made aluminum body cars 30 years before. As did Delahaye and others. Porsche made aluminum body cars from day 1 until the 60s.
Removable hard tops have been around since the 20s.
Ford made aluminum bodied car in the 30 but never put them into production. In the 60s you could get a slant six Plymout engine as a no cost option, Must have not worked out well because it did not last long. Maybe they did not last long.
Here’s more than you probably want to know:
The block was an open deck design (like the troublesome Subaru 2.5 L ), so head gasket sealing was an issue. May have had something to do with them using an iron head, too.
And he put a bar in some of the later models. That Youtube on the other thread is very interesting. Long but I watched the whole thing from used cars to TVs to new cars to tape decks.