GL barrel threading?

I have a GL and recently plopped the money down for a silencer. If you know your rifles you'll know that this isn't threaded. Honestly I'd like to swap put the barrel for something heavier and threaded but I don't have the equipment to do it myself. Is there enough meat on the end of the barrel to thread? I wouldn't be opposed to shortening the barrel either.

Not sure what the muzzle diameter is on those barrels, but this may be of some help in finding the answers you're looking for.

http://www.advanced-armament.com/ass..._01-040513.PDF

Seems like a good bit of info there, gotta get on my computer to see it clearly