new 360 oil pressure problems

I'm working from memory here. Depending on what happened to your block (hot tanked, etc) make sure all the gallery plugs are installed. There are at least three tricky areas

One screw in plug for one of the lifter galleries is INSIDE the block. You must install it by reaching that plug through a larger plug in the rear face of the engine

Next, there is a small press in cup plug in a vertical oil passage above the main bearing. Often this is not removed, but it sure could be.

Last, there are two plugs on the front face of the engine block, covered up by the cam thrust plate.