I can only assume that you have visually confirmed that the spark plugs are actually arcing and that you have fuel present in the cylinders. The only thing left to investigate is the timing. This can only be confirmed by removing the number one plug and turning the motor until compression starts building in that cylinder. Then continue rotating the motor until the timing mark lines up with desired setting or TDC (should not be more than 15-20*). Then check to see if the rotor is pointed to the #1 cylinder and #1 plug wire position on the cap. If it is not, you can restick the distributor to achieve this position or relocate your plug wires to follow the firing order from the rotor position. Most of us have installed the distributor 180* out at one time or another and is the most obvious problem.