Are the doors built different?

[MIPS]

Just an observation I noticed when I was looking for new rust. The fenders and rear quarters have some scratches and stone chips that go right down to the steel but they're being very hesitant to rust out and blister the paint. On the other hand the doors and hatch all have places where there's been a scratch or a stone hit and it's rusting to the point it's blistering the paint off. Internally the inner walls and bottoms of the door are still in great shape so it's just surface rust but was the doors made from a different composition of steel when assembled rather than the galvanized stuff the rest of the body is built from?

[Illeagle1984]

I have read while wandering the catacombs of Den archives that the body was epoxy dipped up to the beltline (where the windows start).  I can tell the doors were not dipped from the last time I pulled a door panel, it was pretty much bare metal inside the door.  Looks like the same galvanized  sheetmetal they used on the roof, I have no headliner and can see that too.  I think the epoxy dip is really tough compared to more modern aka cheaper metal treatments.