I finally decided that I needed to remove the tanks to effectively de-rust and paint the frame.
The only things left are the angle-iron tabs that the supporting metal bolts to, in order to support the tanks.
These supporting angle-irons were originally left bare and never painted.
I'll wire brush them and paint them before putting them back.
The tanks are stacked under the siding.
A token mention of what the trailer originally was - Shasta.