Car has 117k. Stainless exhaust and no cats from headers back. Recently cleaned pcv. Oil smoke only under full load WOT but seems to be intermittent . Not rings. Compression good. Valve-guides? Again, it’s hit and miss. Fresh fuel and some injector cleaner car behaves just fine for a few weeks then a bit of blueish oil smoke 2nd to 3rd on backroads about 65-90 mph. Then clear and smells more like burning off carbon buildup. Just curious. Seems to be a thing with a few early 350’s

 

First, your exhaust is irrelevant, what exactly are the results of your compression test? How many miles on your oil?
If the PCV doesn't rattle when you shake it, replace it. If you are stating improvement in the smoke after injector cleaner- Bingo! Get the injectors professionally cleaned and tested and Uber to work. GL!

 

Compression test isn't useful.

Get a leak down test done.
Then come back.

More than likely rings but it made a difference on my motor when I did the valve stem seals.
Have a look on yt for vids showing signs of valve stems, and then some on rings, it'll probably help identify it some more. Or get a friend to follow you and film it.