Tom,
I've two remaining ideas:
1. a groove worn ito the crank on the rear seal journal
2. Marlin's suggestion regarding crankcase pressure. Excessive ring blowby will create excessive crankcase pressure. If you are running too hot of a cam for the PCV system to function, I might suggest you experiment with a vacuum pump on the crankcase. If you have plenty of intake manifold vacuum at idle, you should be utilizing the pcv system.
George
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