Let's do some quick maff here...
New Colt average price on GB is $1000.00.
After you replace the barrel, bushing, slide stop, mag catch, ejector, firing pin plate, sights, hammer, sear, disco, strut, grip safety, mainspring housing, pins, trigger, thumb safety, various springs and grips that leaves you with the following.
Slide, frame, grip screws, grip screw bushing, guide rod, recoil plug, extractor and plunger tube, sear spring, plunger tube spring, mag catch spring and firing pin...for $1000.00
Now, you can't leave the slide to frame fit the way it is, you would never be happy with that. And you know you don't have the skill to weld or peen it properly yourself. So you have to send it off to someone else who can either weld and machine it to fit or accu-rail the frame to slide. That cost you an additional $250.00 minimum. Now you are in the same Slide, frame, grip screws, grip screw bushing, guide rod, recoil plug, extractor and plunger tube, sear spring, plunger tube spring, mag catch spring and firing pin for $1250.00...
On the other side of our quick maff is this...
New Caspian Slide: $245.00 (Over runs can be had for $150.00)
New Caspian Frame: $215.00 (Foster can be had for $150.00)
Grip Screws: $10.00
Grip Screw Bushings: $10.00
Guide Rod: $20.00
Recoil Plug: $10.00
Extractor: $20.00
Plunger Tube: $10.00
Sear Spring: $8.00
Plunger Tube Spring: $2.00
Mag Catch Spring: $2.00
Firing Pin: $15.00
$567.00 plus shipping (figured at actual retail prices)
OR
$407.00 if you go with Foster Frame and Over run slide!
And this is why, ladies and gents, rebuilds almost always cost you more than a fresh build...and the slide to frame fit will still never be as good as a properly fitted one on new parts (except accu-rail, which is pretty awesome for rebuilds).
Furthermore, if you get started on that rebuild and suddenly realize you have an issue with that "whatever brand" slide that came from your donor gun now you have to replace it!
Just some thoughts and quick maff for you all to think about.
And for what it's worth, it is my opinion that original fresh builds on "builder named frames" always hold and appreciate their value more than rebuilds. That's why so many guys have gone to having frames made with their names on them.