I have been watching this thread with as much puzzlement as Paul when he posted it. I have been looking for things in common with the 2 rear cylinders. Oil pools at the rear is a possibility but good valve seals should run submerged in oil so that is not a definative answer. The problem seems to lie with heat & load as per your 1st post. ie. when you drive it easy there is little or no smoke but when you get it on a bit the problem occurs almost immediately. The fact that the cranking compression is over 10% higher on the 2 offending cylinders suggests an excess of oil inside the cylinders. The leakdown test suggests the rings etc are ok. Very puzzling!! So I ran the problem past one of the top Aussie muscle car specialists, still no definate answer!! So back to heat & load, did you get sonic test #s for all the cylinders, could there be some bore distortion under load when it is hot?? The hardblok fill should eliminate that but if there is any weakness at the thrust faces it may show up under load. I hope that is not your problem but if everything else checks out ok something has to be causing it. Sorry for a long post with no definate answer, but I have a couple of ppl working on ideas, maybe something will come up soon.
Best of luck
David
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