I built a Truck camper in 1969, 1970
It had aluminum roof and aluminum siding.
I went to several house trailer (Mobile Home) manufacturters... found one that would sell me aluminum off their coil... two of the pieces were 20' long.
... they rolled it with the grouves and the pittsburg felt (edge connections) I got two colors... white for the upper half, the nose of the cabover, and the rear,
and brown for the lower half to match my truck.
I made a large tube to haul it home.
I went to Fruhoff Trucking (where they repaired tractor trailors) they sold me a piece off heavy aluminum like used on the top of long trailers, 20' long and 8' wide. It was hauled home as a roll.
I also bought screws, roll caulk, etc from them.
I paid cash both places.
2003 Lance 1161,/slideout/AGM batteries/255W Solar/propane generator/Sat dish/2 Fantastic Fans/AC/winter pkg
AirFoil, Trimetric, LED lights, Platcat vent heat
2003GMC K3500 LT/Crewcab/duramax diesel/allison/dually/4x4/OnStar/front reciever mounted spare