The 95 Chevy motorhome chassis I've been working on recently has 10-lug wheels, and disc brakes all around. It might be worth looking into adapting the rear brake rotors and caliper mounts from one of these rigs to the spindles and hubs of your oldtimer. The spacing of the caliper brackets might be pretty close to the right size. Don't know whether the lug bolt circle is correct or not.
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!