340 Engine Shake

"Surges" implies a fluctuation in engine rpm.
I'll stand by the pump relief valve opening and closing. If you had a bad ground the other gauges would also bounce around.
You have other problems to solve first
Take them one at a time, if you make a bunch of changes to quickly you'll never get figured out.
I still want to see the plugs.

You're right. I'm getting overwhelmed with my mind going to different possibilities. Here are the pics of the plugs. I took these a few days ago.

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