The cowl is the part of a car body between the engine compartment and the dash face. The cowl includes the firewall, cowl top panel, and upper & lower dash panels -- but not the dash itself. For the Datsun 1200, the cowl is where fresh air for ventilation is drawn
See
Body for the sheet metal (firewall & cowl top) Bonnet (hood) for engine covering Cowl Top Grille Ventilation