My 3 pennys worth
DC10 Combi Pax had lifts (2) down to the lower lobe from the main deck galleys 4 and 5. At the rear of the downstairs galley was/is a sliding door into the fwd lower freight hold. Could be opened either from freight hold or lower lobe galley. The lower lobe galley being loaded with galley carts via the fwd. freight door.
Airlines I remember were World, Laker. Air Florida, Eastern, Wardair and possibly CAL -10's.
B707 had a trap door from cockpit into lower 41 and thence a door into fwd end of the fwd freight - never knew why, fire I guess.