Safari was missing the tiny galvanized black water tank located directly under toilet, (never had a gray tank) when I purchased it a month ago. There was a vent pipe, made of some kind of super light plastic, originating from the side of the flushing pedestal that the ceramic toilet sets on and running up the outer corner of the bathroom wall to vent thru the roof.
I know what you mean about the confusion locating inlet and outlets on the black water tank. I purchased a 25 gal tank, rectangular tank which has an outlet below an overhanging, upper portion of the tank. This overhang allowed me to position the tank perpendicular to the trailer so that it drains on the driver's side and doesn't protrude out past the shell. I will have to modify the belly skin to accomodate support straps/framework but I was lucky (?) since this section had been removed at some time and reinstalled.
At this time, I am considering using a tote along for gray water, when I absolutely have to.
Since gray water isn't hazardous, to the best of my knowledge, I will just drain it to the ground when conditions permit.
Please keep posting your progress and ideas. I will do so, too.