On cold start up do you hear any rattling or thumping from the engine?
Rod/main knock is very distinctive.  If you don't, that's good.  What
happens if you drain the 10W-30 (5W-30?) and replace it with 20W-50 or else
put a can or two of STP in the crankcase?  If the oil pressure comes up and
stays up, loose bearings are looking good as a cause.  With the viscosity
modifier in the oil, and on cold start, does the oil pressure go to the peg
or almost so?  This would suggest the pump is okay if it does and point at
the bearings again.  If the oil pressure doesn't go to the peg on a
relatively cool day, it points at the oil pump.

Whichever it is - bearings or pump, drop the pan on this bad boy sooner than
later and swap out both.  Zero oil pressure for even a few seconds is bad
news.  I have not tried this on a late model small block but on early small
blocks it was possible to change out rod and main bearings without pulling
the engine.  The one-piece rear seal may make this impossible.  Has anyone
reading this swapped bearings in an L98 or LT-1 without pulling the engine
or dropping the crank completely?

Charlie Funk

But without a proper operating gauge, if you ever hear the least bit of
tapping
or knocking shut that sucker down right there and pull to the side of
the road.

Who knows if the idiot light still works if the gauge isn't.