I have a 1970 f100 with the original 360 in it. When I first got GHOST [the name I gave my truck] it had a few oil leaks in the engine. The Main spot where I have found oil leaks is where the intake and head join under the valve cover[see arrow].. because the valley pan causes a slight lip on the gasket for the valve cover.. On my engine I had to grind the lip down and use a little extra silicone on all four corners.. just lightly grind it to be as flush as possible the use a small amount of the silicone to fill any gaps.. I hope this helps someone out..
If your worried about fuel prices a Big Block Ford is not for you...