The entire engine "proper" was painted dark gray. Acorn nuts, both manifolds, gasket edges, oil filler cap on post '48's, bellhousing, dipstick, even the bracket from the water pump to generator. The whole shebang was assembled before painting.
Black items include the draft tube, distributor, coil, fan blade, generator, starter, foot starter assembly, and I'm probably forgetting something off the top of my head. "Thriftmaster" was also painted on the valve cover in yellow with a stencil, not the decal like the vendors sell.
Although you'll get disagreements, the 4-speed tranny in my '51 was painted black. It had some factory inspection marks that were on top of what was left of the paint.
Granted the paint wore or burned off some of these items pretty quickly, like the exhaust manifold, gasket edges, and acorn nuts.
Bob
