M Owner,
Here are a couple of ideas...When it cuts out at high speed or under load, see if it clears up a bit when you pull out the choke a bit. If it does, there's some fuel flow problem starving it when it needs more fuel at higher RPM. If not, I'd guess ignition. Did you add a new condensor? Probably not the problem, but maybe. More likely you could have a distributor cap that's arcing from one tower to another (sometimes you can see carbon traces on the inside of the cap that give away this problem), or an old, worn distributor shaft that sprays sparks about anywhere when it starts turning fast. It's also possible there's a problem with one of the new plug wires, assume you're using copper stranded wire and not carbon core wire? Those are the first things that come to mind. Try the above tests. Try wobbling the distributor shaft (should be fairly tight) and try subbing out old plug wires for new, and post back if that still doesn't isolate the problem. Good luck with the old guy...
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