A guess. it's trial and error
Symptoms sound like
1. vacuum in fuel tank
2. Fuel delivery pump filter.
3. jets in Carburettor
4. Ignition COIL or distributor [mainly the cap]
5. Bad or loose earth/s.
Solutions/Tests not necessarily in order.
The reasonably easy first.
1. Run engine with fuel cap off see how it goes. No different!
then replace the cap and go to the next test.
5. Look in the engine compartment to see where the battery earth is terminated also the engine earth make sure neither has started perishing at the bolt attached to chassis/engine
Ok not that still running rough and stopping next test!
4. Ignition coil test get a plug lead tester from car spares shop. work from one end pull a plug lead off the plug and fit the tester in the lead. Plug tester complete with lead on to the plug and run the enging watch for the spark in the tester window until engine dies out. Carry out the same for each plug.
If the spark is weak and inntermittent then it could be the distributor cap faulty or the rotor arm. Buiy new cap and rotor arm.
If the spark on each tested lead is strong and doesn't deviate jump or spark intermittent
then It's got to be
either 2 or 3, the carburetta or the fuel delivery pump.