Pete
On the older motors there are pipe fittings on both sides of the thermostat housing. Others have a flat area that can be drilled and tapped for pipe fittings.This will supply hot water to the intake; run the outlet hose from the manifold, behind the valve cover to a "T" fitting in the heater hose circuit. This is about as clean as you can get. I've seen them run under the engine too.
