360 engine vibration

I agree on the compression testing.... pulling the plug wires one at a time and sensing a drop does not tell you that all cylinders are firing evenly.

The next thought along that line is the compression numbers that you reported earlier, which I think were 150 psi? If that is the case, then perhaps the pistons in there are not stock pistons. A '78 360 motor is a low compression motor, around 8:1 static CR, and that typically would run more like 125-135 psi. If the pistons are different than stock, then there is a good possibility that the balance is all wrong inside. So, please re-run the compression tests for this reason, and to check for consistent compression between all cylinders.

One observation on the TC: I am a bit puzzled that there are NO weights anywhere visible, or any drilled holes in the outer flange or any other other evidence that the TC itself has been balanced. I keep looking at the 1st pix in post #48 and looking at the upper left area of the TC flange and seeing what looks like a place where a rectangular weight might have been. But I cannot really tell. Bottom line: Is the TC balanced?

And, as the OP has suggested himself, the cam may be toast on a lobe or 2....