https://electricgt.com/shop/1967-1969-gm-a-body/
https://electricgt.com/shop/gte-413-ecrate-system/
These guys supposedly do an electric crate motor. Although I doubt that it's plug and play. They don't mention anything about where the batteries go.
On that note, the batteries are the weak link and the "final mile" of technology that they have not resolved. Imagine how fast the Tesla would be if it didn't have a 1,200lb battery to lug around. The equivalent of a full minivan's worth of people. So I'm thinking: how much stored energy is used just to move it's own batteries around? Whomever developes a new battery will be the world's next trillionaire.