Have you checked to see if there is voltage at the fuel pump relay? There may be a blown fuel pump fuse.
Otherwise; try disconnecting the wiring harness plug to the oil pressure sensor; and see if the motor will then start. Some GM oil pressure sensors cut off power to the fuel pump when there is no oil pressure. Disconnecting the wiring plug makes the circuit act as if there is normal oil pressure all the time. If this makes the fuel pump run; your sensor or wiring may be defective.
This problem could also come from the anti theft system, or the anti theft relay.
It may be that the timing chain has broken or jumped out of synch. A cylinder compression test will confirm or disprove that.
Have you actually checked for spark from the plug wires; or are you just assuming there is no spark because it doesn't start?