Does it ever start hot or must it cool down first. Any intermittent running when hot? Maybe the ignition coil? You don't want to do this with a hot engine but if you have an old spark plug wire and good plug, disconnect one of the wires at the distributor, connect the test wire and plug, use a clip lead to connect the plugs ground electrode to a suitable ground on the engine and have someone turn the engine over. If you don't see a spark it could well be the coil. If you do, you can move on to something else. Put your test spark plug wire between the coil and distributor and try to start.

Wouldn't hurt to start gathering new plugs, rotor, cap, and wires.

Tobit.