106214 is for sure original finish. The crud around the selector is a mix of grease/ rust, but really the photo looks a lot worse than it is. That would be the one I'd pick over the others.
7781 looks good, but the finish on the gun does not match the dings on the stock and the different shades would lead me to think it was reblued....but not recently because of the dried oil on the receiver. Or the stock was switched out? Hard call on that one, and the photos are not that great.
8327 should be priced much lower.....it has nothing going for it by comparison.
David is correct, don't fix what ain't broke! Lots of aftermarket parts are marginal. I've never touched any of mine and they all work fine. I have guns in all three finishes of the guns discussed (including one that was refinished) and the only one I'd be sure about is 106214 based on the photos provided.
Side note Ingram M6's did not ship blochy, but some are now. Mine is not. HTH