Robbie,
Wakejunky responded with some very pertinent information, the main thing being that the oil pressure reading will not affect whether or not the engine runs, it is a display thing only. He suggested checking the valves to see if you bent them when replacing the cam belt/rebuilding the engine. He suggested checking the basic stuff, ignition/fuel. The fuel pump would be one thing I would look at carefully, it could have been damaged if there was water in the fuel. Do a search on this board, there are some posts by Capt. Rick and others addressing how to t/s the fuel pump.
Pete