That would be an interesting challenge. I'm the same as you I really don't like seeing these old bangers getting scrapped. In saying that totally understand the economics (and labour) of rebuilding something in this condition.
I have never seen rot like that in the top parts of quarters before.
Probably sat under a canvas or cloth tarp for years. Cars rust in odd ways when moisture is trapped in/on them for a long time.Same here, both sides the same. it is very odd.