Not sure what the finish of the hardware was but from the production films I have viewed the "front clip" was installed as an assembly and both the body and front clip were already painted.

I can't testify to every GM plant but the KC plant I toured in the late 60s as part of GM training painted sheet metal parts separately then assembled them. From the firewall back was dipped in primer then painted while the fenders, valances, etc. forward of the firewall were primed and painted separately. The fasteners were not painted to my knowledge. Of course there could be exceptions I'm not aware of. I've not been to every plant in every decade of production. Generally speaking, if the parts were bolted together before painting, it would leave bare metal at the joining edges which would promote rust. The reason the quarter panels weren't painted separately like the fenders is because they were welded in place rather than bolting. They were then leaded at the seams, processes you can't do to painted metal.

Tiny and Steve,

Thanks for your responses. I suspected that this was the case but needed some validation. My 51 was painted once some time in its life and the bolts fastening the fenders to the body have the blue body paint on them. They appear to be original fasteners being indented head (untrimmed) and all the same. The finish was probably originally cad or zinc plating as many of the other bolts in the front end are. I have the ability to replate fasteners and I think I will do these over the winter.

Jeff

Update: I removed the bolts and found original blue paint under them indicating that the fenders were painted prior to assembly. I also found plating (silver) on the underside of the bolts. I have replated them and reinstalled. Thanks for your help here.

Jeff