Make sure that all of your spade connectors inside of the distributor are not made with too soft of brass. If any of the connections are loose and you find that you can easily mash the female spade connector tighter, you may find that to be your problem.
I ran into that scenario with a Accel HEI distributor. Those slightly loose connections will wreak havoc on an HEI. They seem not to like stray electrons randomly milling about.
Another thing to check is the tachometer wire (if your distributor has one). If this wire even comes close to a ground it will cause a random misfire. If it finds a good ground, it will completely disable the distributor. Hotrodders are known to utilize this wire with a kill switch to prevent theft.
