At the front of the engine 'A' is the the heater return pipe under the inlet manifold. 'B1' is a port on the front of the inlet manifold that is an internal pipe travelling through the inlet manifold to near the back where it is open, which goes to 'B2' on the back of the front cover. 'D' is the top hose to the radiator:

'A' is a short hose from the heater return pipe under the inlet manifold which tees into the large bottom hose port on the pump. April 2025: Fitted the spare when the inlet manifold was off as the existing one seemed quite hard, and had to shorten the manifold pipe end by about an inch. 'B' is another short hose from the front of the manifold to a port on the back of the front cover. 'C' is the pump inlet from the bottom hose, and 'D' is the top hose from the thermostat housing to the radiator:

The port on the back of the front cover for the 'B' hose comes through towards the pump at the arrow, and the slot bounded by the ellipse:

The pump body is flat where the port comes through the front cover at the arrow, so coolant flows along the slot in the front cover (the ellipse) to a hole which goes through into the large port for the bottom hose:

The yellow arrow indicates direction of rotation i.e. the vanes are drawing coolant in from the bottom hose and the radiator and pushing it into two ports at the bottom of the crankcase. This will also pull a small amount of coolant from the hole in the ellipse i.e. through the front cover from the 'B' hose and the pipe internal to the inlet manifold and is a bypass to circulate a small amount of coolant through the block and heads while the thermostat is closed. The steam-pipe between the inlet manifold and thermostat cover: