Leon,
How does it run with the PCV tube disconnected and the intake manifold port plugged? This is not a solution, just a diagnostic, of course. I'm running a PCV on my 1954 261 similar to yours, but with five Strombergs - two primaries and three secondaries. It idles fairly well with about 16" of vacuum. Has the ignition timing been checked and set? I've seen incorrect timing cause problems that you describe.
