Sounds like you've done a couple throw-parts-at-it things first. What about basic tune-up? Plugs, wires, careful wire routing, distributor cap, rotor, clean & set points, correct base timing/mechanical advance/vacuum advance, vacuum leaks, distributor wear & play, timing chain stretch, decarbon engine, all grounds and ground straps present and clean, voltage regulator functioning correctly, engine compression balanced within specs?

Need to know more details about what you're starting with and the condition it's in to really attempt to advise.

If after confirming all of above is good, and you're still 100% confident it's an ignition problem, then there is no better way to diagnose and find the problem than to find an old school mechanic who owns and knows how to use an Ignition Scope for a diagnostic.