I have been struggling with the same thing for 11 months and may have got to the bottom of it. The two jumper wires in the distributor are woven cloth covered. they must have been the originals. After looking very closely, i found a bare spot where one had grounded on the inside side of the distributor. The other one flexes slightly when accelerating and too had lost its insulation at the bend. I had tried EVERYTHING. New coil, metal threaded spark plug wires. New points, condenser, plugs, rotor and cap. The coil i bought was a flamethrower from pertronix for 6v and had to have special ceramic thingiy in the line to the coil. all new wiring everywhere into the switch. Then I saw these two wires in the distributor. Taped them up and the car did great!!! I have since replaced the whole distributor with a spare i had that had been rebuilt 50 years ago. I tuned it with a vacuum gauge and it starts and runs flawlessly now. Timing light was useless compared the the vacuum gauge.
The whole point of my story is it probably something really really simple. just keep working thru the pieces one by one. keep a record of what you have replaced. I wrote down everything that was involved and checked it off as i went thru it. I have pulled out almost every hair (and there isn't much) on my head. If it were not for the help from this group, i would not have got thru this. You will get it! Don't give up