Thanks Power Surge, I'll try to answer all the questions:
-I did compare the two stocks side-by-side. With the rear internal cutout of the stocks exactly even, the tip of the stocks were also even (so, no dimensional issues).
But the cross bolt in the problem stock was positioned more than 1/8" further forward than the crossbolt on the jungle stock. This 1/8+ difference has been mentioned in some other posts I've since dredged up on-line about this problem.
- The flat part on the cross bolt is facing upwards on all cross bolts, as I believe they're supoosed to be. And besides, I don't think rotating it could cause any worse of a fit (since it's basically a circle), but i was thinking if i rotated it so the flat part was facing backwards, it might be the equivalent of shaving off the 1/8" I need. I dunno, does that make sense? Unfortunately, I haven't been able to test the theory, because I don't have the 2-pronged tool necessary for securing part of the bolt while I unscrew the other side with a flat-head.
- I'm pretty sure the barrel wasn't machined down, since it doesn't have the original sight post on it. It has an aftermarket post (great little unit form Prince50/BulletButton !) that is made for the larger diameter portion of a cut down barrel, which eliminates the need to lathe-down the barrel (and by extension, the need to remove the sight block).
I believe he (gunsmith) just cut the barrel, crowned it, and then installed a prince50 sight.
So, going by what I'm seeing, and what I've since run across from several sources, it appears that I do have a stock made for a long-collar rifle, and short of jacking it up with some semi-major surgery, (which I'd prefer not to do, for fear of just wrecking an otherwise nice stock), I'm stuck with a stock I can't use.
I posted it last night on a couple local classified sites, at $45 or some x39 ammo, but no bites yet. (I didn't really expect any, especially since i came clean on it's compatibility issues).
Anyway, thanks for taking a few guesses, I appreciate any advice or info I can get.