That makes sense Walt, after reading this in the Assembly Manual:
"Chrome Wheel (Optional): Paint outboard vertical surface of brake drum assembly per Buick Spec. 345 prior to installing he chrome wheel. Paint must not enter the brakes around the backing plate."
It would be nice to know what Buick Spec. 345 is. Probably black, but who knows? The chrome wheels on the 65 Skylark had silver centers, so I guess it's possible the drums were painted some shade of gray. But black might be more likely.
Thanks for that Walt. More support for painting them black. We'll see.
Chuck