I've got a 95 Z28 that run just like yours does. I rebuilt it last year and she's built right with a new Melling high volume oil pump and all new bearings throughout. When cold, it runs 65psi and after warmed it will idle at around 25 psi, and back up to 60 psi anything above idle . LT1 I have always has valve train noise. I As far as you 1980 Chevy making noise, it may or may not be a problem. Try and rule out all you can before more drastic measures are taken. Like Rrumbler said, it could just need the rockers readjusted.