Finally checked out Frontier Wheels (Duluth, MN) after seeing their lot on my commute for months. They keep around 105 vehicles, mostly sports cars and coupes. They were totally fine with my mechanic doing a once-over, which honestly settles half the trust question.
Lot address: 1602 Motorsport Dr, Duluth, MN. Visitor parking: Front-lot customer stalls facing the office; overflow on the side street near Duluth lot gate.
Paper side: licensed with the state (looked it up), about 99% of stock has title in hand per the office, and they offer a 3-month/3,000-mile limited warranty.
Overall: good people to deal with. 13 years in business around sports cars and coupes, doc fee $249 and it's on the window sheet, no games. I'd send a family member there.