4 Wheel Drive/SUVs: 1995 GMC Suburban, oil pressure gauge, worst case scenario

Question
I have a 1995 GMC Suburban, with a loud rattle or tick, I thought the cam was wiped out, but the rocker arms look to be moving fine, what I did notice was very low to no oil comming out of the lifters or rocker arms. The oil pressure gauge on board shows 40-50 psi with no change. Looking for some spots to check.

Answer
Jaytee,

I know this may be a dumb question and there is no offense meant but 1st, does it have the right amount of oil in it since it will show pressure with as little as a half of a quart in the pan and how old is the oil filter?  One problem spot on these is the intake gaskets leaking oil/ antifreeze. or the oil pump could be going bad worst case scenario. The tick is definatly in the top end as you saw but finding the actual problem will be the tricky part.

Send me any more info you have as you know

Matt