It is most likely the intake is not sealed.
Some folks will run a thin bead of RTV around the water jackets at the head and intake... as well as the gasket of course.
Presure test the cooling system with the oil drained, the drain plugs out, and the nose jacked high, if it's the intake you will get water out of the front and the back of the pan, if only comes out the front it could be the front (timing) cover gasket leaking. If after presurizing the system for 30-45 minutes there is no signs of water I would guess it is either from a bad head gasket(s) or something you got in there during the gasket replace.
If your head gaskets are bad enough to get water in the oil you should have other symptoms, and this test would not result in any water imeadiatly noticable in the pan as it would take a while to get past the rings.
If you suspect head gaskets, DO NOT start the motor after this test as it could result in a broken piston or worse. Pull all the spark plugs and turn motor over to see if any water pumps out of cylinders or out into exhaust, then do a compression check.
you may be fine, when you replaced your gaskets some coolant might have found it's way into the gully and then down into your oil. if your oil still comes up milkly after some more driving then you should use some silicone on the manifold gaskets. don't worry it sounds like you'll be okay.