318 Poly Vibration

That's normal condensation on the dipstick and in the valve cover. Why not actually try some diagnosis instead of just throwing parts at it? You said you made no difference grounding plug wires. Guess what? You didn't ground them successfully! Had you done so, each time you grounded a wire, you would have gotten a dead skip.

Run a standard compression test first. You can do that for FREE! Go to your local big box auto parts store and rent a compression tester. You get all of your money back when you return the tool. If it has a compression problem, that will pick it up. Screw a leak down tester. That's more for testing percentage of leak down when comparing cylinders. Not necessarily what you need here.

Do the compression test.........or keep chasing your tail. It's your choice.