I would look into the heads first.

The 350 I used to have in my truck drank a bottle of oil a week and had two plugs that would get sooted up real bad requiring me to rotate them around. Interestingly the truck never blew any smoke out the exhaust unless you floored it, and even then it wasn't very much.

I did a cranking compression test and it pulled very close to 150 on every cylinder so that eliminated the rings.

I pretty much assumed my issue was related to the heads, either the guides or the seals, but I never really dug into it. What was weird was the engine never really used oil and then it suddenly started using a lot almost overnight.