I was thinking more about pulling it out to check the bearing clearances, more so for inspection purposes. If you pull the #3 main cap, #3 and #5 rod bearings you can check for excessive wear and use plasti-gauge to see what your bearing oil clearances look like. You could also see what the cylinder walls look like (good cross hatch) with the oil pan off and make sure nothing funky is going on with the oil pump/pickup. You've got to figure out the oil pressure problem and most likely can't figure out why with the engine in the car, unless you've got a bad sending unit and have more oil pressure than you think. I'll ask again, before you pull the engine, is this a mechanical aftermarket gauge with an oil pressure tube/line or factory/aftermarket gauge with an electric sending unit? 3 lbs. of oil pressure at idle should bleed down the lifters and make all kinds of clattering.