Oil spewing out of the breathers.

[Trevor]

Chuck, it would appear that you know exactly what you are about and everything put forward so far is simply telling you "how to suck eggs". I hope you have not been somewhat offended.

My interpretation of your post, was that you are aware of the obvious possibilities and are seeking thoughts on any oddity you may not have thought of. I am confident that you would be awake to any cause for a direct link between inlet manifold and sump.

I gather you now have no positive crankcase ventilation. You have not reported as to the exact extent of the oil discharge. Could it be that what you are experiencing, is what can in fact be expected in view of the age of the engine?

Is the overhead gear receiving too much oil and the return facility therefore inadequate? Possibly this is so and the ventilation is in part, working as a siphon?