Depends on what kind of passenger traffic you want to do - and which engineers and Guardian goodies you have unlocked. Assuming short range in-bubble trips, no engineers or Guardian modules, doing it for the money (or positive rep/inf), I'd use something like this:
A ship builder, outfitting and comparison tool for Elite Dangerous
s.orbis.zone
For longer range, in-bubble, replace the first class cabin with a fuel scoop. For expedition and Colonia trips, put a size 5 scoop in a size 5 slot and put a size 4 SRV hanger in that size 4 slot, maybe replace (some of) the smaller cabins with cargo space, AFMU and a repair limpet controller.