It sounds like the engine is being starved for fuel. Somewhere in your fuel delivery system you have a problem. Either you have a blockage, or your fuel pump is about to go out on you.
You need to narrow your problem down to a system, The hit or miss thing is not working.
Start with the basics of pre-computer diagnosis,
Check these out in a systematic manner
. See if you have spark, pull a wire off of a plug, hold it close to a metalic object and have someone roll the engine over, if you have a good strongsparkwhen the engine is not "running" (wont run), then you can eliminate the ignition.
Again, when the car wont run, look down the carburator, and open the throttle a few times, if the carb is pumping fuel into the carburator (accelerator pump) then the carb is getting fuel to it, you have eliminated the fuel pump and linesas the problem. Even if the carburator is still suspect, the car should at least fire if the accelerator pump is dumping gas into the manifold. (do not try to start the car while looking into the carb)
Put a timing light on the car, if the timing is on, this can be eliminated.
By doing this, you can at least narrow your search down to a single system, either fuel or ignition.
It seems as if everyone is pointing you in the fuel direction, they may be right, and they may be wrong...... pretend like you are doing an internet search,,,, narrow your results,
or, just keep changing parts helter skelter and fixing things that aint broke.
Also, if the car is running, and suddenly dies, without stuttering and such, I would say that it is not a fuel issue,,,,, if you are still in the changing parts mode, change the coil, they are cheap enough.