oil pressure problem on rebuilt 1978 350

i have a 1986 truck and i bought a 350 bottom end from a guy and he had a local machine shop do all of the work. it has a 490 lift cam 64 cc heads, and i am concerned about the oil pressure. it has 10w30 and a fram tough gaurd filter the engine was install about 700 miles ago and there is not any knocking sounds when i start the engine in the morning it is at 45 psi and when it warms up it drop to 15psi and then it will only get up to 30 psi through out the rpm range is this normal the pump is new the only thing reused from the old motor was the oil pressure sensor from the old engine the bearing are new and it has been magnaflux and everything what do you think the problem is?

well Matt sometimes the oil pan can be to close to the pickup screen, or the pan not deep enough. But you can check the oil to make sure the pump is working , if yopu have an old distribitor take the shaft and atach it to a drill and pull your dist. out and put the shat in and turn on the dill remove a vaule cover and make sure your getting oil up to the rocker on all the rockers