Dies after 2 miles, why?

I have a 73 Duster with a 408, FABO ignition and TQ. Had it all together several years, runs great, low 12's on low octane pump gas. Been running fine for 10,000 miles. I recently have been keeping it in storage, only driving it once every 2-3 weeks.

Last weekend, I primed the carb with the electric fuel pump, pumped the gas 3 or 4 times, and she fired right up. I let her idles for 5 minutes or so while I moved the other car into storage and closed everything up.

I got on the road, about 1-2 miles from the storage location, 50 mph, and she dies. like she lost fuel completely or lost ignition. Coasted her into a gas station, fiddled around for 5 minutes, and she started back up, and after 3 miles of very rough running, she straightened out and ran fine for the next 30miles. Back into storage that night.

Went and got her today, almost an exact repeat of today, and she died with 100 feet of the same place at 50 mph as last time, spit back a few times, and managed to get her started while still rolling.

I had her in the garage for about 7 hours. Fired her up for a drive around town, and had an exact repeat again, died about 2 miles from cranking her up, and would not fire! Pulled her off the road, pulled the air cleaner, an had plenty of fuel coming from the accelerator pump, with fumes in the primary swirling around. After 5 minutes, whe fired up and I drove home, no other problems!

I am fairly sure it is an ignition problem, but swapping the ballast made no difference. Anybody experienced this before? I have replace the fuel filter, (just to be sure).

Note that she has run fine for 3 years, and never exhibited this problem. I have not changed anything.