Here are a couple of things to look at.
First, look at the rocker shaft pedistal at the back of the engine. There should be a screw on the passenger side holding rocker shaft staionary. If that screw has come out, the shaft can turn such that the oil passage is blocked. On the two 1500 engines I have, that screw has been missing from both.
If you pass that test, pull the rocker assembley and the dizzy and dizzy drive gear. Use a reversable drill with a long slot head screw driver attachement to turn the oil pump counter clockwise. Let it run for several minutes. If all is well below the head, eventually oil should bubble up through the oil passage in the head.
If you pass the first two tests, dissassemble and check you shaft assembly. Most likely you will need to replace the shaft and rockers. I just bought a set at spitbits.com. They seem to have the lowest prices, and the quality and fit is pretty good.
If you fail the second test.... on Terri's car, the problem was that one of the previous engine rebuilders had failed to replace the plug on the oil line that feeds the head. This plug is under the timing cover in the upper driver's side area on the front engine cover. Without that plug, all the oil intended for the head pours into the timing cover and back into the pan.