Oil from Exhaust Port

So i've noticed a small dribble of oil coming down the side of the engine case right underneath the #6 exhaust port. I had originally thought it was a leaky valve cover gasket, but now I think it's coming form the actual exhaust port.

I did a compression test. Don't recall exact numbers now, but #6 was significantly lower than the rest. I put a teaspoon of oil in the spark plug hole and it did make the number jump a bit. Am I looking at a worn out ring here or a leaky valve? I bought this motor a little over a year ago, apparently rebuilt, and have only put about 6 thousand miles on it since then.

The van is running fine...no noticeable loss of power and it is not smoking at all. Should I just keep an eye on it? Any advice?

pulled spark plugs?? any oily?? if not -ill say valve cover gasket again!! dont use a rubber gasket too!! Cork only & seal to cover only!! 

I my book no need to worry about compression if running smooth--not a perfectionist. However, because the engine leans back a bit most of the oil that leaks around the valve cover gasket (most leak something) will flow back to the rear of the engine and then down the engine--especially if van sits more than it runs. And, please resist the urge to use RTV or some other silicone sealant on your valve cover gaskets because just a little glob of it sucked into you oil gallery can do mucho damage.

I agree with the other poster as it's unlikely to be coming out of exhaust manifold as it really burns too hot inside and outside for oil to pass as oil will burn before it accumulates from getting past the pistons rings.

I say turn up the radio, open the windows and drive. My 2 cents anyway.

Having been an auto mechanic for more than 30 years, what you are describing
is caused from the cyl having an oil consumption issue, weak rings or even bad valve
guides and or seals, I have seen bore than one 305 leak oil from an exhaust port.
How bad is your oil consumption?