1967 Ford Econo Supervan 240 Buckin and back firing

Hey Guys.  Looking for the obvious I guess.  

Van was running great.  Doing about 55 on the hwy for 20 min.  Starts buckin like it's not getting fuel.  Ends up stalling on the side of the hwy.  I give it a few minutes then fire it up.  It runs like normal for about 5 min then starts bucking again followed by some serious back firing.  The bucking and back fire is intermittent at various speeds.  I limp the poor thing home.  I'll try to trouble shoot the easy stuff, but unfortunately I don't have the knowledge to be working this issue out.  Just curious as to where my friends at the shop will start.    

Thanks for the help.

I wonder if the float/needle valve in carb is sticking, fuel filter condition, fuel pump. The fact that it seemed to run normal again for a period when you fired it back up would seem to indicate it's not in the timing gears or valve train to me but I'm certainly no expert on the subject. Could be an issue with the ignition system, bad coil or module, I'd verify spark on all cylinders when it's displaying the problem. Is the van a manual or Automatic transmission, if auto, does it only happen when in gear?

,,,you could put a clear piece of fuel line or a clear plastic fuel filter temporarily between the fuel pump and carburetor to see if fuel is getting through,,,,,,is that a Loadamatic distributor,,,,,,,run the engine with the distributor advance unhooked,,,see if problem goes away..... are the points adjusted,,,,,,,,do you have a dwellmeter to see what the points are doing when all the drama starts?

Id certainly review the points, the condensor, the button inside the distributor cap, the rotor, the coil wire, maybe replacing all that stuff....sometimes the coil can break down internally when it gets hot and its hard to test, may have to put another on and run it again, I know you hate to shotgun parts at it but intermittent problems are really hard to diagnose..backfiring is usually caused by something firing/not firing at the wrong time.

Also the wire between the distributor and the coil on mine is laying, rubbing on the block, could have a wire shorting to ground?

Im skeptical about fuel issues unless the sock in the tank might have gotten plugged up? I dont think the fuel filter would act like that but then again they are cheap too...If the sock in the tank is plugged up I have temporarily relieved that by blowing air pressure back down the fuel line to clear the debris but obviously its gonna still be in the tank and you would have to drop the tank and clean it if that were the problem.

Any recent maintenance performed leading up to this? Just trying to rule out the easy stuff.

Thanks very much guys.  I'll be getting some help with this in the next couple days.  I'll consider all of your suggestions.

Mechanic told me that the Flux Capacitor was faulty.  Found myself on top of a clock tower waiting for Marty to get the Delorean up to 88 mph.  

Just kiddin...weak / inconsistent spark re: points / condenser.  Sounds like it fried the coil.  New coil and electronic conversion kit = fun summer with the family.  Runnin great.  

Thanks guys for the help.