"There is some strange 'plumbing' on the engine."
I am not sure exactly what you mean by strange plumbing.
Remember, the plugs are in the valley between the runners of the intake manifold (if you ever take a plug out it is very important to make sure the valley is clean first--you do NOT want junk and plunder falling down into the spark plug hole--don't ask me how I know).
I see hoses that provide hot water to the heaters/defrosters in the bus. The hoses on the curbside go to the step well heater/defroster and the hoses on the street side go to the heaters/defrosters on the street side of the bus. The route the coolant makes is going out in the black hose on the street side, it returns in the red hose to go out the curb side, and returns in the black hose where it goes back to the engine.
I see the top hose to the radiator going to the thermostat housing and another hose going from the thermostat housing to the water pump.
I see a gas line going from the fuel pump to the carb.
I also see a vacuum line going from the back of the carb which will be going down to the hydravac power brake booster which will be on the frame rail below the driver.
I am not sure what other plumbing there is that you find strange.