I'd have to agree with ulflyer, if it's all correct, it's a great deal. It looks a lot to me like the guy got a CMP carbine that had the stock ran through the big dishwasher, the seller then added a little BLO to the stock. The pictures don't show enough to persuade me that it's worth $800.00, even with a spare bolt added to the package. It could well be an after production bolt, yes to USGI specs, but it does nothing to make the carbine more correct. If it's a Underwood bolt with all correct internals, maybe.
The ad I linked to from SOG offers Underwoods at $695. They're returns from Israel, and they have the reputation of taking pretty good care of their guns. Add to that the fact they likely were sold to them fairly soon after WW-II, and may well be pretty correct carbines.
As to the one Husker_Fan was talking about, if you can get that carbine at the price you believe you can, buy it. That "mismatched" Rockola recoil plate is worth around $100.00 itself.