Yes, If you were to investigate the cars' chassis numbers and race history, you'll find they were original cars built and raced in period. Some of the cars in the race were pretty significant examples as well.
In period, most race cars were one-offs or factory-built race cars made in small numbers. The Bugatti Type 35, and its later update the 51 were made in hundreds. They were fast, and you could actually buy them.
I know they are grown men...but racing these cars is incredibly dangerous. I think the cars should have the basic mods to keep the drivers alive. At least a roll bar.