My '66 Trade Wind had the same bunch of wiring although I believe a PO wired it. A couple years back I was cleaning out the front over head storage and something told me to look behind the face panels to the right and left of the doors. Behold there were speaker holes cut into the inner face...I suppose if the front was 'taken' off it would expose the hole...about 6" in dia. They don't appear to have been cut by anyone but Airstream.
Neil and Lynn Holman
Kirk Creek, Big Sur, Ca. coast.
1966 Trade Wind
1971 Buick Centurion convertible
1969 Oldsmobile Ninety Eight