383 running like s#%t.

What is "good"? and
What is "not so good"? and
Why did you abandon the test?
Your methodology is strange. Especially since the problem popped up like a light switch, as per post #1

With a "good" compression test, it is rare to see a "not so good" LD test. To abandon the test after just one hole, is to assume your LD tester never makes a mistake.
Why are you so gung-ho to take it apart. It could just be a piece of carbon stuck on a valve.Or a pumped up lifter.
I suppose it could be a bad head gasket. But again; Finish the LD test to know.