What I meant was, you said you had a strong spark from the coil....was this strong spark noticed right out of the coil with a test wire and spark tester, or was the strong spark coming from the spark tester installed at the end of the wire that goes into the distributor? This is the first place you should be checking for spark.....
If you have a strong spark out of the coil, and a weak one from one of the ignition wires, then it's either the cap, rotor or wires.....you say it's a new cap and rotor, and installed correctly, so that leads me to the ignition wires....
Like Blue suggests, get a good test wire and attach it to the distributor at #1, and attach your spark tester to the end of it to see if you have a strong spark(should be the same as out of the coil).....