I suspect your help so far is right on track. I had this problem for a while, but no longer. Unfortunately, I am uncertain what the reason was, but here's the things that seemed related:
1/ Intake manifold needed to be planed. Angles were off and one port was higher than the rest (easy check with a straight edge).
2/ I used Sealed Power rings vs Hastings this time. Very different
oil control expander. I credit this change to be the most significant.
Things that were not responsible (but could be):
1/
Oil flooding. I always had restrictors to the heads. If you don't, keep in mind the engine sits at a slightly raked back angle and the rear valve guides could be swamped with
oil.
2/ Oil drip trays not installed. I have run with and without these trays. Smoking didn't change regardless.
3/ Detonation. This causes the top two ring gaps to align. I personally doubt this could cause enough oil to enter the combustion chamber, but others say otherwise.
4/ Type (brand) of intake manifold gaskets. I've heard about problems with one brand vs another, but if the angles are right any should work. I use Fel-pro, blue-seal towards manifold, gasket shellac on both sides around water ports.