The Steinwinter Supercargo (opens in new tab)

That one's explicitly mentioned at the end of TFA itself, though.

Not the OP but I know the feelings about the Citroen BX - it was just such a drab design, looked like a shipping box, and was just generally a dull car to be around. Best feature was its suspension, which would lift the front end up during acceleration until it got to a 'settled', floating position .. that always kind of felt like doing light speed in the millenium falcon or something similiarly odd in a very, very boring car.

It's a bigger issue than one of legality. The high seat in a standard truck cab offsets two of the biggest challenges with driving a truck: it takes ages to get up to speed, and a very long distance to stop. High visibility gives better sight lines for further so the driver can plan. That helps to improve fuel efficiency by better anticipating traffic and planning acceleration accordingly. It's absolutely vital for safety because the driver needs to brake for what's happening a huge distance up the road. If you don't have that line of sight, they'd have to drive so defensively ("stop in the distance you can see to be clear") that any efficiency gains from the aero would be completely swallowed by all the accelerating and braking.

A sports car of course can stop in a heartbeat and the excess power means it can easily manage its flow in traffic. They'd perhaps not even be legal if they took as much road to stop as a loaded truck. It's four times the distance - 150ft for a decent sports car at 70mph; 600+ for a semi.