I'd stop. Especially if it was an interesting old car
True story -- I was travelling on a divided highway and passed an older 911 on the other side of the highway that was in obvious distress. I exited at the next interchange (2 km or so) and headed back. By the time I arrived, there was also an MGB, an Alfa Romeo Spider, and an E30 BMW all pulled over with their drivers offering assistance. None of us knew one another.