How much trouble am I in?

A little backstory: my '69 Barracuda is a very long-term project that I work on when budget and enthusiam allows. About ten years ago I rebuilt an '86 318, mainly to get the roller cam and 302 heads for a mild cruiser engine. I installed it but didn't fire it because the car had no wiring, cooling, exhaust, etc, so I taped all the openings and let it sit while I worked on the rest of the car. I used plenty of assembly lube and sealed it up.

Last summer the car was ready to support a running engine so I pre-oiled it, got oil to both rocker shafts, and it fired immediately. Hallelujah! Wasn't concerned with a full break-in with the roller lifters, so I ran it about ten minutes to check for leaks and overheating. Everything looked and sounded good.

As of a few days ago the car will move, if not roadworthy. I idled it out of the garage and noticed a small leak from the oil filter adapter. It made a little puddle that looked slightly milky. ****. Pulled the dipstick and it is showing some milky streaks. Not a full-blown milkshake, but there's some water in there. Keep in mind the engine is "new" and clean, with only a few minutes of run time. Oil is clear, and I'm using the yellow universal coolant, which is much the same color as the oil. I ran it long enough to open the thermostat, and I couldn't see any compression bubbles in the radiator neck. No white smoke from the exhaust.

I am seriously bummed. This thing is so close to finally being back on the road, and the thought of major engine problems makes my stomach hurt. Any chance it could be condensation from being in an unheated garage all this time, or it that just wishful thinking? Change the oil and filter and see what it looks like after a few minutes? Help me out here.