The L1011 FAA approved cargo conversion leaves 1 of the original pax door operable but removes the slide and replaces it with an escape rope.
I guess the answer is that unless you have a combi you cannot carry "passengers" in the airline sense of the word.
The passenger are technically all company personel and there is a normal pre-flight procedure to give the supernumaries a briefing on all emergency equipment ( as in pax aircraft) but given by the crew rather than a hostie. ( come to think of it ....
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