I think non-functioning guns are legal, especially if they are fake guns. Sounds like a fun project. You're probably going to want to still do an engine swap though. An old V6 plus a couple hundred pounds of steel won't play together very well.
Note, if I've gotten any facts wrong in the above, just ignore any points I made with them
don't believe a thing you read about the next gen Camaro -- as history has proven time and time again:
WE DO NOT TALK ABOUT FUTURE PRODUCT PLANS PERIOD FbodFather
Camaro5 Fest sub-forum