OIL LEAK from top rear of motor...HELP!!

[CEE1NG_RED]

The PO installed a '78 350 small block motor in the '67. I had the gasket changed from the valve covers and intake manifold, but it still leaks oil at the top rear of the intake manifold despite the new gaskets installed. My buddy, a mechanic, says that the PO put silicone in that area. He noticed that the block had a slight slope or groove like a hole where it connects to the intake manifold, but it is not a crack nor a hole on motor/block and suggested that the intake manifold may not be an exact match for the block (eventhough it sits flushed, but there is a small groove/slope like a screw on the back of the top block where the manifold bolts to) that's why the PO put silicone on it as a temp fix before I purchased it. So for the time being, he put silicone on it as well til we get this figured out.

Anyways, he did not take a pic of what he was trying to explain to me, but maybe you guys/gals can shed some light. The area is near the oil pressure sender (but no oil is is evident on the sending unit).

Is there anyway I can identify the intake manifold (by part# or brand) so I can determine if it is made for my '78 chevy 350 motor. HELP please!!