most mill spec parts won't interchange so you'll be SOL if you need parts.
View Quote
The only parts unique to a Colt are the .170 pin FCG parts. You can buy them anywhere, even Bushmaster sells the whole Colt FCG kit for $49.95:
[url=http://www.bushmaster.com/shopping/lowers/arcoltkit.asp]Colt FCG parts kit[/url]
The only other thing you'd ever have to worry about is mating a large pin Colt lower to a small pin upper. There are plenty of inexpensive adapters available that will take care of this. Here are two of them:
[url=http://www.bushmaster.com/shopping/lowers/we-003.asp]Adapter from Bushmaster[/url]
[url=http://store.yahoo.com/cdnn/arunfronconp.html]Adapter from CDNN[/url]
Some people don't like the protruding sear blocks on some of the preban Colts. You can either mill it off if it bothers you or keep it like I did. There is a pic floating around here somewhere that shows that the sear block doesn't interfere with the installation of a full circle carrier. I'll try to find the pic and post it.
Good luck with your purchase. Don't be afraid to buy a preban Colt, a Bushmaster, or any other rifle with a proven track record.