My 66 has a vent of sorts under the trailer from the floor where the refer sits. It also has a lockable door right behind the refer to allow access. The vent has a grille to keep out stray dinosaurs and a PO installed a filter there. I assume to keep down the dust. There is a vent in the floor behind the refer, just keep looking.
1966 Mercury Park Lane 4 DR Breezeway 410 4V, C-6, 2.80 - Streamless.
1966 Lincoln 4 door Convertible 462 4V 1971 Ford LTD Convertible 429 4V Phoenix ~ Yeah it's hot however it's a dry heat!