The new pump I posted the picture of is $130, a junkyard pump is about $50 with the pulley and whatever bracketry you can pull.
I'll try and get a pic of the stock setup later, but it's just hung low on the right side of the engine by the lift pump, and driven by a belt off the alternator.
The 7.3 turns 3400-3800 rpm, and has a much larger lower pulley so it actually spins the belts faster than the OM617, so the pump should be good for the higher rpm of the Mercedes diesels as well.