If I remember correctly, doesn't the Perkins
have 2 square drive threaded plugs at the top front of the engine. Delivery
to the heater
comes out of the cylinder head
, and the return goes in just below the thermostat housing. Haven't worked on 1 in a while, so this ain't gospel.
have a nice neat double-T fitting, with a built in diverter reed that may help you.