AS A TEST, I removed and plugged the suction hose containing the PCV valve from the carb base. So now, what I have is:
1. Old road draft tube hole in rear of block STILL connected to air cleaner housing via stock Chevy 1" hose.
2. After removing and plugging 3/8" PCV hose from oil fill tube at front of intake manifold, I installed a temporary piece of filter material from an old breather filter to cover the nipple.
So the crankcase is vented to atmosphere at the oil fill tube, and vented to the air filter housing at the draft tube location.
Took the car for a 130 mile ride where cruising mostly at 50-70 MPH. Took engine at WOT to 7500 RPM three times. Took engine to 6000 RPM in 1st gear a few times and closed throttle. Never saw smoke out the back (not that I had ever seen any before, so no change here).
Got home and removed plugs. All 8 dry. What I did find this time was evidence of oil in the air cleaner, which was completely DRY before.
Now the question: How do I modify my PCV system so it doesn't suck oil? Can I use one at all?