My oil burning pig. Pics too!

How in the world can you be making crankcase pressure, with two breathers?!
I would take those breathers apart and check for 1-way valves.
Were those breathers on the last motor-that ran fine?
or are those new to this engine?

Or was that pressure test run with the engine sealed? In which case..Color me red.

I ran evacs and muffs on a mild 360. They worked really well. Too well! I ran them straight off the baffled valve covers, and at higher rpms they pulled oil right through, and sent it out the dual 3inch tailpipes. Rather than build a better oil-separator, I went back to the pcv system.

To do a topend oiling test,you know about clocking the cam,differently for each side, right?

Black oil is part of the reason to run a PCV system. But its usually a symptom of; fat carburetion in one or more circuits,driving style,driving cycles,engine running-temp, intake temp, weak ignition, you know , all that tuning stuff.