Started working on the door. Got most of the paint off and started to explore the rust areas in the lower corners. Need to cut the rust out and figure out the best way to fix the holes. I'm sure these are typical rust areas for A-body cars. I'm wondering what makes them susceptible to rust in these corners and how to reduce re-occurrence.

My original door was completely rotted away in the front lower corner, so I bought this door from a guy in upstate NY where it had sat in a barn for years. .It needs a lot of work but it's really not too bad.
I will be installing new lock cylinders and new (or good used if I can find) door handles after car is painted.
Also, I had installed late seventies F-body mirrors so I would have functioning mirrors. F-body housings are slightly wider than my originals but the mirrors seem to be the same size as my originals which were frozen. I am going to attempt to put the guts from the F-body mirrors into my original housings (which are nice). I need to finish getting the F-body mirrors apart--need to drill out one screw. We'll see.