I had same problem
see my post "misfire at cruising speed"
after hunting down the problem and exhausting every effort i decided to pull the distributor (MSD digital E curve) and install my old standby mallory unilite.
upon pulling the dist I noticed the gear kinda looked funny.
seems like it is wearing oddly.
I removed the gear and drove to the local speed shop and got a replacement bronze gear.
Keep in mind now that my dist had less than 300 miles on it.
anyhow I replaced the gear and reinstalled dist.
problem went away!