tts, Didn't you say you used the same intake manifold both times - the one with the missing shield screws in the bottom?

You indicated you had oil inside the intake mainifold plenums and under the carburator - how would bad or unseated rings cause this? Do you have a crankcase breather plumbed to the air cleaner, or a PCV Valve - I think you said no? How else would oil get inside the intake?