that's a pretty good price (I think, but then again, my opinion and a boarding pass might get you on the 'plane).
long ago and far away, i found a really nice stock at a show, and i got the price down to (if i recall) twenty five bucks ... long story short, I already have a renegade in flint, and i wanted another in .62 smooth, but the stock had a 15/16 channel and the Renegade uses a one inch barrel ... out come the chisels and sandpaper, and it's off-to-the-races and "presto" the stock now fits the barrel (or the barrel fits the stock, depending on your grammar).
A few flea-bay visits later, i was the owner of a few new barrels: a pretty nice looking .54 in Percussion, and a .54 that was honestly advertised as being "in less than pristine condition." (That's latin for "sewer pipe.') But the rusty one was destined for a trip to Bobby Hoyt to be made into a .62 smooth, so if some of the shavings are oxidised, I'm OK with that.
Now here's the tricky bit: the breech plugs on the flint and the percussion are a bit different. Do not panic: the lengths are the same (or very close) but if you put a flint breechplug on a percussion barrel, you will need to do some pretty fancy timing to get the flats to line up, and the top flat to align with the hooked breech, and the breech face to bottom out in just the right place. I used a plug from track of the Wolf, and it is slightly oversized, and took a few days of tinkering to get just right, but at the end of the tantrum, the plug was correctly aligned and the hook breech lined up where it was supposed to go.
HOWEVER, the plug I got from Track is oversized (about 17/16 across the flats) so i had to file it to fit with the rest of the barrel ... you see where this is going - now i have to drawfile the rest of the barrel and reblue the thing. (the sights, underrib, keyways and so on do come off, with a minimum of flailing around - just remember, patience is a *&%@ing virtue).
And you'll need a new touch- hole. You can go with the usual tap (it's a 1/4 x24, i think, but don't hold me to that) or you can do what I did and get a White Lightnin' touch hole liner. i personally like the White Lightnin', but unless you're a competitive level shooter, which i'm not, i don't think it makes a huge difference. Go with whatever works for you.
so, to get to the short answer to your question, you can do this, but it will take a good bit of tinkering and thrashing about. Whether or not this is worth it is of course a question only you can answer. If all you want to do is shoot, i'd say probably not, but if you also like to tinker with stuff, it might be a way to go.
As far as the lock, i can att4est to the interchangeability of the old and new style of flintlocks, as well as the percussion: they will all fit into the same mortise.
Since you're throwing money around like the proverbial drunken sailor, check out the Deerslayer trigger at R.E. Davis - money well spent, IMO.
Good luck with your project, and
Make Good Smoke!