4540help

Hello everyone. I just joined the site and hope I can some of the other members can help me with a problem with my engine.

It is a mid 70's 454 in a el camino. I have owned the car for 15 years but havent driven it in the last 5 years. I would crank it every so often and let it run. I decided to start driving it again. First thing I did was change some parts. New fuel pump,fuel filter ,carb ( holley 750 ) and a new Mallory HEI dist. The car starts as soon as you turn the key, but runs really rough. It pops back through the carb, and surges a lot. When I put a timming light on it, the timming mark actually moves back and forth about 2 inches, almost like the damper is spinning on the crankshaft. I have pulled the dist 3 or 4 times , just checking to make sure I have it right. # 1 cylinder up on compression stroke and the dist rotor lined up with # 1 on the cap. The dist is in correctly. I was running short on ideas, so I took it to a local guy that has a shop. A block away from his shop I had to stop at a stop sign. When I stopped, the oil light started flashing. Once the engine picked up 50 RPM's the light went out. The guy at the shop pulled the sending unit and put a gauge in. He says the car has no oil pressure at idle, but it picks up with RPM. He thinks I have a bad cam. I am not so sure. I think I have two problems. The erractic timming mark is a puzzle to me, since the car cranks so easily. As far as the oil pressure, I may know what the problem is. Just before I bought the car in 1996 , the guy that owned it had a problem with the oil light comming on when stopping. He pulled the engine and found that the screen had come off the oil pump. He welded it on, and it has lasted 15 years now. I just wonder if the screen has once again come off.
I know this is a little long, but the more information you have, the easier it will be to help me out.
Thanks in advance.
Kevin

I just finished a compression test. This test was done with all plugs out. The engine was 150-160 degrees. I used 4 cycles for each cylinder. Also, this was a dry test. Between the headers and the factory AC system, I can only get oil in half the cylinders so I only did the dry test.

1 - 125psi 2 - 130psi
3 - 130psi 4 - 125psi
5- 150psi ( I ran this one twice ) 6 - 135psi
7 - 125psi 8 - 140psi