My Espar D5WS is mounted under my Sprinter on the driver side, about midway between the front and rear wheels. The heater mount is affixed to the inside of the body, just above the pinch seam and the heater clips into this and is secured with one long bolt that goes through the heater and into the heater mount.
My fuel pump is just forward of the heater and the exhaust hose with the muffler is attached just above the pinch seam and runs to just before the rear driver side wheel.
My hydronic hoses go from the heater up through the floor into a cabinet on the driver side of the van, about midway, which is where the hydronic pump, reservoir tank, liquid/air heat exchanger, and liquid/liquid heat exchanger are mounted.