Oil Leak Question

Are you 100% sure it's coming from the intake gasket? The reason I ask is I had a 340 that started leaking oil at the front of the motor and the fan then blew it all over. I had the intake gasket changed thinking that was where it was leaking but I still had oil everywhere after a few miles. I took it back to the mechanic thinking he didn't get it sealed good. He checked the gasket and didn't find anything wrong. He then took the dipstick out, held a piece of cardboard behind the tube and held the engine at about 3000 rpm for a couple of minutes. Pretty soon you could see little drops of oil blowing out onto the cardboard. So the oil was coming out of the dipstick, not the intake! I never did find out exactly why it started doing that (it was fine for 4-5k miles). My mechanic and I are sure it has too much crankcase pressure but a leakdown test didn't find anything wrong. Wasn't overfull on oil, either. It also didn't have any noticable blow-by. I finally 'band-aided' the problem by putting the tall later ('89) dipstick tube and dipstick with the cap that went over the tube (with a piece of thin rubber tubing over the outside of the dipstick tube so the cap would seal) and it doesn't blow oil out any more.
And, FWIW, I had a 318 that blew oil out the dipstick like a gusher. It quit when I cut the plugged exhaust off the car.
Don't know if any of this helps but it's food for thought.
Dallas