OK, I think I answered this "proof" question before, but I will have a go at it again. I don't remember what I said initially, but maybe this will be a more refined answer.
Jim's "proof" might be accomplished by a highly evolved, advanced being or group of beings, which I would not define as "God".
BTW, I put the odds of the existence of ludicrously advanced beings much higher than a supernatural deity. Though, their "powers" might appear magic to us just as our technology might appear magic to Cro-Magnon man.
Proof of an Abrahamic God would have to be specific, IMO. I think a series of very detailed prophecies which came true,
indisputably, as described would probably do it - these prophecies would be communicated to me by direct brain input - telepathy. That's how "He" works sometimes, yes?
When I think about that answer, I guess anything defined as "God" could probably do the same, not just the Abrahamic God. I'm also assuming the lowly, highly-evolved beings would not have the ability to predict the future.
I think the personal telepathic communication of detailed prophecies which later indisputably came true would most likely make me a believer. Of course, no one would believe me, so I would write the prophecies down
after they happened and then tell everyone the true story . . . and everyone would think I was crazy. And then, a few thousand years later . . .
My 2¢
Now bring on the "gotchas".
Best,