Water in oil after rebuild - looking for guidance

My Magnum 318 just developed an internal leak that I'm trying to find too. I have the Edelbrock intake and LA front dress on it. As of now, I know that I lose coolant and I have mayo under the valve covers and in the PCV system. The dipstick looks like clean 300 mile oil. I've pressurized the cooling system to 13 psi (it's a Champion radiator with 0.9bar cap) and I lose about 2 psi in a half hour on a dead cold engine. Other than checking for loose intake and timing cover bolts, I haven't done any more research. I tried thumping on the intake and timing cover with a nylon mallet while looking for a pressure drop and saw nothing. Wondering if it's leaking out of timing cover into the timing chain area, leaking under the intake, or a head gasket. I'm going to try pressurizing and hand rolling the engine over to see if I get anything out of the spark plug holes next.