Grigg knows what he's talking about... good advice.
I would speculate that they were "squeezed" rather than driven at the factory. It would be faster, the results would be consistent, they could be set without heat, it would only require one worker and the noise level driving rivets with a gun would be insane.
During my years in the aircraft industry I've driven more rivets than I can remember but never anything like a 3/8-inch steel one. I'd plan on practicing a lot, they are not going to go down without a fight.
Unless you are intending a "restoration" I'd recommend just using bolts... that's essentially all a rivet is anyway.
