The stock by itself is worth, in my opinion, $400-500 as it sits. No, the $600 does not include the stock.
Given the issues with the gun, I'd want to see those grips in person to make sure they are not reproductions, but if they are real they are perhaps the most valuable thing on that gun.
Everything about the rear sight parts, base, etc. screams "issues" to me. To be frank, if this gun were offered to me at almost any price, I would pass on it. Faked/humped/butchered collectibles aren't really my "thing".
It's not a collectible that's for sure.
If the grips are fakes at least they did a good job, it's strange how the reproduction people can't get the "9" even close to the original font.
The stock looks authentic as well.