The white panels are just the mocked up body. It will be aluminum skinned with copper rivets. Upper curved portion door top up will be steel cut on cnc and painted bronze or black. Lower section ( wood in mockup ) will be ribbed , aluminum and either painted or raw. Not gonna mirror polish the aluminum skin or corrode it. Just planning on the as bought fairly shiny finish if it presents well. Framing under the aluminum skinned mid section will be 1x2 square tube. I'll probably insulate a bit between the skin just in case but it'll stay inside so not super worried about moisture. Been mocking up the dash area with a 54 olds center gauge I like alot and a crazy cut down 66 Impala wheel. Delayed a little in the start of the final body due to the virus. I rebuilt a canned ham trailer for an elderly club member last year , he is insisting on returning the favor ( and a really really good fab guy ) but I don't want him out and about much in this mess as he isn't super healthy. All in good time.The Aeroliner looks a bit Winnebago-ish now with the white panels.
So copper, aluminum, steel for the body. add a little moisture and you get some serious corrosion or galvanic reaction. Dissimilar metals like to attack each other with water as the fuel. Consider some sort of insulators between the metals so all that work doesn't disintegrate within a couple years. There is an interesting book on the topic: Rust: The Longest War by Jonathan Waldman