Another oil pressure question!

I have a 1989 Chevy 454. Oil pressure is at 30 at idle and pinned past 60 on highway.when I first got the truck it stayed at 60 on my 6 hour ride home. What/if should I be concerned?i guess I'll replace the oil pressure switch first.what should I look for next? Thanks

Put a Manuel gauge on it and see where it is.