"Can't say for all aircraft types,
but those I'm familiar with that have ram air, the ram air inlet is a naca inlet somewhere(usually lower fuselage),and the ducting by-passes the air-con packs. "
Unfortunately, there is nothing like this on a 767.... other than the Naca scoops for the aircon pack heat exchangers (However, this air doesn't go into the cabin). The bleed air from the engines which is used by the packs... and the air being sucked in by the Naca scoops doesn't mix... It's more like a car radiator (where water and air don't mix).
Regards.
Q.