Ok, lets go back to my first reply and dig a little deeper. "Are you getting good blue, not orange, spark at every spark plug when it will not start?" Also, as I mentioned earlier, P0300 is almost always caused by a fault in the secondary ignition system. There are other things that can cause it, such as the MAF sensor, low fuel pressure, and sometimes a TP sensor. Those may or may not set a corresponding DTC in memory.
How many miles on the distributor cap and rotor? Do you know what brand they are?
How many miles on the spark plugs? Do you know what brand they are?
How many miles on the spark plug wires? Do you know what brand they are?