2000 Silverado 4x2 issues

Maybe you folks will have a few answers to my issues... I have a 4.8 v8 in my truck.. 185k miles (lol). For the most part my truck runs fine. Its basically stock with no modifications other then
bigger tires and a very small lift (about 1" taller then a 1500HD) basically leveling it (you know how they sit lower in the front).
Problems: pinging...pretty audible actually. around 1k-1500 rpm you can hear it. Dont know if there is a fix or not...only a irritant unless I blow a hole in the piston. lol.
Oil pressure gauge/low oil pressure. I've started seeing this recently.. it got pretty cold the past 1.5 weeks and in the morning my truck is at 20# but after it warms up its at 40-43#. I dont know whether to attribute this to the weather or to a faulty gauge.
I prefer to have this thing run for a few months before I decide to put a 6L motor in it.
TIA
Alex
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...sure is acting backwards from expectation, huh? Almost like an oil pump drive shaft in an old engine is slipping when cold & *catches up* when warmer. s
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