01 Silverado 2500HD-Oil pressure question

[Stayinalive]

Hey my fellow truck fans! First time poster here. Just joined.
I am back in a truck but have a question. I recently acquired
this beauty and it only has 45k actual miles on it! Got it for a steal
but after about two weeks, the love goggles unfogged and I noticed
a knocking upon start up. After a few minutes it would go away
becoming quieter and quieter as time went by. When I would step on it
it would knock also.

#2
I noticed the oil guage in the dash was fluctuating from 40-60 when
accelerating and when you settle on a speed (40-70mph) it sits in the 50's.
Is this normal, what should the pressure be. what are the top 3 things I should
go fix before getting into the big stuff? I dont think its the oil pump for some reason. Maybe lifters?

Thanks for any feedback, knowledge given.

Richard

[Crank]

Generally my '01 Silverado with 6.0L has a cold start knock as well. I'm about to break 160K on my truck, and I'm not a bit concerned for that knocking noise. As far as I know, all the LSX truck motors do it pretty much. I wouldnt pay no mind to it, if you have good oil pressure, leave it be. I've heard its something to do with the intake, I've heard piston slap. Either way, it aint hurting my truck.