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

Try a mechanical gauge as suggested to get around any electrical effects.

I've run synthetic for at least 1M miles in all sorts of uses, including racing. Low pressure does not worry me.... I have raced 4 miles with zero oil pressure with Mobil 1 (blew an oil fitting) with no damage found at teardown. (I have a witness.) IMHO it is step backwards to move to non-synthetic.

There is a 15W50 Mobil 1 that should help the pressure if it is not a gauge issue. And probably other synthetics that are heavier; I just don't know them all.