Tap the holes in the hub for some flat head machine screws and countersink the holes in the drums for a flush fit of the screw heads. Problem solved, without using spacers or modifying the wheels. I believe the original rivets were 1/4" diameter, which is exactly right for a 5/16-18 tap- - - -no drilling required. A drop of blue LocTite on the machine screw will keep it secure without a lock washer or a nut on the back side.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!