Water in oil dipstick

So I'm running the motor after getting gas into it and noticed that there is water pooling in my dipstick. Also, when the vehicle is idling for more then about five minutes, it starts sounding like a train whistling under the hood. About a week ago, I blew a radiator hose and replaced it, filling the radiator with mainly water, because of the situation. So, now I'm stuck. I'm thinking it's a blown head gasket, as the vehicle sat for twenty five years before I finally brought it back to life. Any advice? I'm starting a full engine tear-down tomorrow and am interested in what other possibilities may be going on. It's a original dodge 440 motor in a in a 1977 Dodge m40 commander motor-home.