Here's a copy of  an original Arnolt brochure for their heater.
 Very few of the heaters left today still have the name plate
 above the main opening..




Here's the brochure image showing the installed heater plus a view of the plumbing
under the bonnet.  Note that the heater does not sit on the tunnel carpet.  It is
actually suspended slightly above it.




Here's another under-bonnet view.  This plumbing uses the Arnolt adapter that
replaces the bypass hose.






Here's a view of the heater showing the mounting hardware attached to the
back of the heater.  The mount is triangulated to hold the heater in a
cantilevered manner from under the toolbox with an arm that bolts to the
underside of the battery box  (location shown in next image).  The thin
piece at the top of the mount slips into a slot that is on the underside of
the toolbox.


This view shows the location of the bolt that secures the mounting bracket arm.
This also shows the grometted holes for the hoses.  The piece of wood that the
 battery rests on is relieved to provide clearance for the bolt head.