First the holes: The lowest and most forward hole is for the stock oil pressure gauge connection. The small one in the rear is for the coolant drain cock. The other one on my engines has a pipe plug in it. If that one is in a water jacket you could return the water from your intake heat to it. I think you could put a T in the heater hose from the water pump and run it to the manifold and then from the manifold to either of the rear holes. make sure the big one is water.

Be careful about banging on the crank snout. Dampeners should be pressed on and off when possible. You can damage the thrust bearing on the main bearing, the one that limits crank end play. Check the end play to make sure you are still OK. I've never ruined one but it can be done.

"I wonder if God created man because he was disappointed in the monkey?" Mark Twain