I finally installed the metal header. It is held on by lots of nails, and also the joints at each end are soldered. I used stainless steel nails, which I found by accident in the hardware store. I also figured out how to use a bit of rubber tubing to seal around the hole where the windshield wiper goes, so that rain would not get into that hole and start rusting out the inside of the over-windshield area.
I started working on the header area back in April, so I am glad to get it (mostly) finished. I still need to put some filler in the joints on each end, to get a smooth contour between the header, the windshield pillars, and the roof.