Yup, chivveee was the only one to stamp the frame. GMC only did the door posts. As for what you should make it, well you can probably guess my vote
It looks like someone shrunk her down a little though. If you don't know for sure how it was done it might be worth a look for safety's sake. Lots of kids go after them with a torch and welder and they'll fall apart on you at 65mph. If its done well then at least you'll know. That's a good lookin truck!