How about running your line starting at the rear drain on driverside to the manifold, then out of manifold to the thermostat housing? Higher pressure at drain outlet and lower pressure at T stat housing. You can also use metal lines.
The small top fitting on waterpump is the "Bypass". This would normally go to the T-Stat housing. Really only needed for the HD use these engines endured in working environments. Heavy trucks, combines, Ag equipment, ect.
This would seem to change the cooling of the engine. A little more water to the back, but is part of the engine now starved of water?
