Stainless does not hold paint well without prep, screw paint will chip when installing. Paint gathers in the head recess, PITA. Just use the unpainted screws.
As far as original look: They would NOT have pre painted screws and probably did not paint after screws in place. But others can state if they were or were not painted. Can't paint after headliner in place at factory. I'm not sure screws were stainless steel back then either. Do you have any of the old screws that were in it?

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn