I had two separate misfire problems, first was my 72 340 swinger. It worked good up to about 4800 rpm then started breaking down. Turned out to be a bad coil. Second was on my 70 408 4 speed swinger, the problem was when the previous owner had it, (real good friend of mine). It wouldn't dial up more than 5000 rpm. He had changed everything including disconnect the wire harness and reconnecting each item one at a time and still wouldn't dial up. It turned out being the pick up coil in the distributor. Everyone told us that this pick up served one purpose and one purpose only, to start the car. This info was proven wrong. As soon as it was changed (from an old rusty distributor on the shop floor) the thing dialed up to 7000 for a joke and been doing so ever since.
