Has anybody restocked a production gun? ...
Yes, I have, and have two main observations gained from the experience:
(1)
Unfortunately, by the time you get new wood, a better lock ( especially if the gun is flint), and correct furniture, you basically have bought a kit. And, it is extremely hard to make it look like anything but a makeover...
That being said, I need to explain my perspective regarding rifles:
It's crazy accurate...
If the barrel is good and sound, you can build around that barrel.. whatever stock you like as long as the barrel fits...
Personally, I place a probably inordinate amount of value in a barrel that shoots better than I expect. Barrels that shoot far beyond expectation simply aren't leaving my hands; they're home for life. I mean, it just ain't goin' anywhere, and I'll spend whatever time, money and effort I need to, to get that critter built into the rifle I want out of it.
On the other hand, if it DON'T shoot one heckuva lot better than I'll ever wring out of it, it's not going to spend much time around my house.
As Hungry Horse alluded to, I've got several I've spent way more money getting "personalized" to suit me, than they're really worth to anyone else... simply because they were proven shooters before I ever started whittling on 'em.
But that's just my view, for what little that's worth.