New to me Barracuda with Mopar Crate 390hp low oil pressure

Drain the synthetic. Stick in 10w-something or 15W something and see if the pressures change.
If the PCV cannot handle the blow by, somethings wrong and it's probably not the PCV. From what you are describing, and understanding it's a Mopar produced crate engine originally, I would look at the oil pressure with dinosaur oil in it, and if it's still low, I'd pull the engine for inspection.