2000 rpm you should easily see 50 psi. You still should see
oil off the rocker arms at any psi as this is a function of flow rather than pressure. You may have an obstruction but that would only create more pressure rather than less enless it occured between the pan and the pump. Is it possible you fabricated your own gasket for the
oil pan pick up? Is it possible the pick up is so close to the pan it is not getting
oil? (seems unlikely)
I'd go get a brand new drill from a big box retailer. Lets say one that has the motto "satisfaction garanteed" I'd run that mother until it smoked (hopefully getting you lots of oil pressure).
If the drill doesn't satisfy you return it when you are done. I used a Sears 18v cordless with great success. It really shouldn't be as hard as it has been for you. You mau want to pull the pan and look and see if all is as it should be.
The only other thing I can think of is if the oil pump didn't get properly tightened it might be pushing oil out the mounting flange but even then a fresh pump should flow pleanty of oil unless it was really loose. You really can't install head gaskets backwards and still get the head dowels seated so this is pretty unlikely.
The other scenario is a bad pump. It happens. You may want to pull the pan and inspect the assembly and change the pump just in case.
Rick is 100% right, I left a galley plug out when I installed my 427. I mentioned looking at the floor after you primed right
. Fortunately it was the one in front.