Finally checked out Horizon Auto Mart (Minneapolis, MN) after seeing their lot on my commute for months. They keep around 30 vehicles, mostly classic and collector cars. They were totally fine with my mechanic doing a once-over, which honestly settles half the trust question.
Lot address: 2470 Heritage Dr, Minneapolis, MN. Visitor parking: Front-lot customer stalls facing the office; overflow on the side street near Minneapolis lot gate.
Paper side: licensed with the state (looked it up), about 79% of stock has title in hand per the office, and they offer a 30-day/1,000-mile powertrain warranty.
Overall: good people to deal with. 24 years in business around classic and collector cars, doc fee $449 and it's on the window sheet, no games. I'd send a family member there.