Uh oh, found coolant in the rear intake

[johnneilson]

Do you know the history of this engine?
What are the chances it has seats installed for the valves?

Could it be a head gasket, sure, but it could be a lot of other things.

If you haven't removed the head yet, I would pressurize the water system lightly and check in the port. (20-30 psi max)

Have had port rust thru just below the valve seat area, valve seat crack below the seat, crack thru seat into cylinder, you get the point.

Best of luck, John