If I can remember correctly, I tried to start an armalite project with a CA gen 2 metal body. The mechbox will drop into the body fine and dandy, but it is likely that you may experience problems with full auto. You will be able to switch to and shoot semi fine, however full auto will still shoot semi and/or lock up thetrigger. This 'may' be fixable with a slight modification to the selector plate as shown here:
http://www.airsoftcanada.com/showthr...witch+problems
Cheers