I recently acquired a 72 240Z. In may attempts to get it running, I have noticed a coolant leak coming from the intake manifold area. It is an E88 intake. By putting a mirror under it, the leak seems to be coming from what looks like one of two freeze plugs under the intake port for the front carb. My question is three-fold. Am I correct in assuming that these indentations are freeze plugs and if so can they be replaced and how difficult? The manifold may just be cast that way but they sure look like freeze plugs. I have checked the coolant lines and fittings going into this intake and they are dry. Thank you in advance.