Hang on, this is a 440. I know pretty much nothing about BBs but I have noticed that the valley is divorced from the intake, so it seems to me that it would be impossible for the intake to evacuate the crankcase, as there is no physical connection between them.
But it is still possible for the intake to suck air on the underside of the ports. That's gonna be a tough test.
However, if you still have the previous gaskets, you might be able to see it in the compression-pattern.
The only other places I can think of for air infiltration, are;
in the EGR circuit, if your intake has one;
or a cracked heat crossover, if your intake has one.
