halifaxhops said

Sorry Andy way to many names. It should be ported for the vacuum advance. That can possibly be the issue. I do not remember the amount of vac advance on that one. Just say it is marked 10 on the arm that is 20 degrees on the crank. OK for numbers sake you set it at TDC with a light then hook up manifold vacuum that is 20 right from the start then you start adding the mechanical in as you add rpms, it get really high fast. Is it pinging right before the stumble?

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67Dart273 said

The only problem I would see with ground is if the distributor is tight enough to ground to the block, and the module properly grounded to dist. You might check THE MODULE MOUNTING SCREWS be sure they are not too long and allowing the module to be loose

The battery MUST be grounded to the engine block or it would never crank.

There is no connection to a coil case unless the coil is defective. I see you've got more than one coil, so I can't see that a problem

I am REALLY running out of ideas

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67Dart273 said

Let me add this up. Is this what I understand?

You have two distributors, neither run correct

You have two coils, neither run correctly

You have two (or more) modules and neither run correctly?

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