engine problem

'74 Ranchero 351C. I took my new Ranchero out for her first run. She started and ran fine for about an hour. Then the oil light came on when I took my foot off the gas. After a stop she stopped with a clunk. Cranking the engine caused the selinoid to melt. After the selinoid was replaced she started fine, but 10 minutes later the oil light was on if I was doing less then 40 MPH. She got worse and then stopped with a clunk. I dragged her home and flushed the oil as was recommended as the car had been sitting for 4 years. Now she will only start with a jump and after 29 minutes of idling the oil light comes on and she stops with a clunk. One suggested that I spun the main bearing, another that the oil pump locked from gunk and the flush made it worse, another that the timing chain was about to throw a tooth. HELP!!

You need a new oil pump, or at least check the armature on the pump. It sounds like after the motor has warmed up and oil is up in the motor, your oil pressure drops off. This can come from either bad seals at the pump, or the bearing inside of your pump is bad, either way, replace the oil pump and replace the seals. It also could mean you need to tighten up any bolts on the pump, as the motor warms, the pump might change position relative to the crankshaft, keeping the pump from operating properly.