Well, the cam is advanced 4 degrees already so I do have decent bottom end but a little more never hurts. The leak is at/around the thermostat housing. I've changed thermostat housings a couple times, it now has an old cast iron one on it; and both surfaces have been ground or finished somewhat - has also had different gaskets with/without sealant, currently glued together with permatex. It seems very sensitive to pressure, when the system pressure builds a bit it leaks. The rad cap has also been changed and tested and it's right on 15 lbs. so the pressure isn't unreasonably high. Cold weather conditions like now it's at its worst - not drastic, but have to refill the overflow bottle every two weeks as it cycles from max to almost dry. I can't always see moisture at the housing/intake joint, but it's down in that dip right there which is what makes me think it may just be a porosity issue with the manifold itself. I now have ~ 90K on the engine and it's been doing this off and on for the whole time. I've improved it but cannot seem to cure it.
Mike