The similar trim that runs the length of my 67 Polara 500 was completely rotten. The aluminum does not do well when placed against steel, and rots the quarter panel as well in dissimilar metal corrosion. I don't think your car is in a bad of shape, though. The trim is held on with little steel hairpins that go out from a central hub, you lift the trim up slightly and try to depress that steel wire that snaps into place around the periphery of the trim. Those clips tend to rust, too.
They should have made this trim out of stainless steel, then we would not have so many problems today. GM used a lot more stainless.
If anyone has the knowledge to make these pieces out of stainless, I am all ears. It is just so hard to work with.
The few NOS pieces that I have seen on ebay usually have an asking price of over $200 per piece.
If I were you, I would clean the floorpans, repaint them use POR prep, POR on all of the bare areas. As it gets fairly tacky, dust on some rattle can primer over it from a long distance away, so that you see the gray specks, but you don’t make the black turn all gray. Then after it is all completely dried, prime and paint it in the original color. If you just have a small area that is a little thin and you want to reinforce it, as the POR is still wet and tacky, saturate a little piece of fiberglass cloth in POR paint and lay it down in there. Quiksteel epoxy putty is also compatible with POR paint. Got some pits? When the POR is tacky, cover the pits with Quiksteel. These repairs last quite well if done in moderation. If it needs cut out and welded in, then that is great, too.
These are very effective for removing rust, and they don’t leave you with stainless steel wires sticking you like a porcupine.
https://www.amazon.com/3M-Paint-Rus...rust+removal&qid=1564804976&s=gateway&sr=8-11
They get used up fast. I used to buy them at Wally World.
I would also address that engine and paint the firewall while you are at it.
Then address the rear window. You will probably need a good mig welder, disc grinder, and shrinker stretcher machine. Pre brake formed steel can be purchased. Then I would blend the new roof paint to the existing paint, and above all I would avoid touching that lower trim. Yellow should be easy to match.
New carpet, sealed up glass, new engine, and go drive it and have some more fun!
