Toyota Repair: Toyota 4 runner, low oil pressure, toyota 4runner

Question
I have a 1990 toyota 4runner gas 3.0 v6 automatic 4x4 with 350,000km's. I have very low oil pressure 10 lbs at idle 12-13 lbs when I rev the engine up.  My question is where should I start to determine what could cause such a low reading.  I used a mechanical tester right on the block. Would I have low reading because the oil pump pick up is blocked? Do these 3.0 v6 have oil pumps that typically wear out at 350,000 km's? Are there any other places that could cause a blockage? Would you suggest an oil pump replacement at this stage of the motors life? Is it worth it or should I scrape the suv altogether? Everything else on the 4 runner is in great shape.  I am sorry for not explaing my situtaion more clearly on my last question. I would really appreciate any advise you could give as I have tried forums and this doesnt seems to be a typical problem people with 4 runner at this age and km's are experiencing. I dont want the engine to blow up because I didnt take care of it.  Thank you in advance.  Rob

Answer
It may be an oil pump failure but it's more likely that the oil pickup screen is partially clogged, unfortunately removing the oil pan on the 4x4 is kind of involved you either have to remove the engine or remove the entire front axle in order to remove the oil pan.