Loosing oil pressure ?

Ok heres what happened. I was cruising around the out skirts of town, in my yellow 73 dart, doing about 65 mph when I was cut off by a little old lady. I had to slam the brakes hard to keep from hitting her. I managed to put a hole in the oil pan of my 440. The car ended up sitting for a few months before I was able to put another oil pan on it. Once I did, I had no oil pressure. A friend told me to re prime the pump. I bought the tool to prime the pump with a drill. I thought it worked because I had about 50psi after I was done. I got the dart tuned back up and the oil pressure stayed up the whole time. Well the car sat for another few days and when I went to start it again, NO OIL PRESSURE! What is going on here. If any of you can help me out I would greatly appreciate it.