Any recommendations?

If I had the space+money, I'd go for a Factory Five kit: https://www.factoryfive.com/mk5/complete-kit/

and add an LS drivetrain.

caterham https://caterhamcars.com/en/models/assembly

Do these even still exist? And is it reasonable to get one road-legal somewhere like the U.S. for less than the cost of buying one (once you assign at least some value to your time)?

I'm not in the US so no idea ... but according to answer in Google:

> All Caterham models are imported as rolling chassis. They are street legal in the U.S. under EPA kit-car regulations and can be registered through processes specific to individual states.

source https://www.edmunds.com/car-news/2015-caterham-seven-360-sta...

So, no, then? Even before valuing your labor at anything, they're more expensive than a lot of cars that come assembled.

I'd love a kit car that wasn't ridiculously expensive and/or designed to be raced. But I can understand that the kind of people who would invest the time in building a car would be okay with those propositions.

I wonder if there's a market for building something purely utilitarian, like a little hatchback or something, as a kit vehicle - with the express purpose of learning a lot of automotive principles along the way.