Gentlemen, I obtained a 350 4-bolt block with 125,000 miles and it had low oil pressure. The block looked good so I bought it and had it sent to my machine shop. It was cleaned, hot-tanked and magnafluxed for cracks. My machine shop said it was good and I proceded to purchase a Keith Black Stroker kit from the machine shop. The block was bored .030 and still needed a litle clean-up so it went to .040 and new pistons were ordered. They installed the cam bearings and freeze plugs and balanced the rotating assembly. I picked up the pieces and started assembly. ALL the oil plugs were installed, including the plug under the rear main cap. The front cam plugs were tapped and steel set screws were installed. The main bearings were plast-gaged and the largest two were the number 4 and 5 pistons rods and they were .0030 with the rest around .0020 - .0027  I installed a Moroso Stroker 8-quart pan with a high flow oil pump with a pink spring (high pressure) installed. When I completed the assembly, before installing the intake manifold, I put a used distributor blank housing in with a straight shaft going into the oil pump. I turned the shaft with a 500rpm drill motor and could not get any oil up through the push-rods into the rocker cups. I removed the lifters and spun the drill motor and I was getting good oil flow through the back holes. I dis-assembled the lifters, cleaned, reassembled them and re-primed them. When i reinstalled them, it took a while but I started to get a little drip through each one. When I installed a pressure gage, all I was able to generate was about 8psi. I finished the motor and installed it into the car and started it up. At idle Im only getting about 10-15psi until the motor reachs about 2500rpm. Then I get about 35-40psi. My machinist says I should be getting about 30 at idle and over 40 at 2500rpm. DO I HAVE A PROBLEM?? I think that I should get at least 20-25psi at idle.  The cam is a 248/448 Crane. Timing is set at 10 degrees.  

Cam and timing don't have anything to do with your oil pressure problem.

What did this motor come out of?

It sounds like a bearing wasn't installed properly and one of the oil passages is obstructed. The other possibility is one of the oil passage plugs at the back of the block. Check to see if someone installed any oil restrictors. (Why I wouldn't know, but better to check it to be sure)

Bad news, you're gonna have to pull that motor back out and tear it down to the short block. I'd check the bearings too, running on low oil pressure might've done some damage.

Another possibility is with the oil pump. Try putting a stock pressure spring in your pump, and spin it with an oil pump primer, see what pressure you get.