Some of the details of the outgoing Presidential Limo which are fairly obvious just looking at it, is that it is not your average Cadillac. One detail that was released back when it was new, is that "The Beast" is based on a medium duty truck chassis. It's basically a Tank on rubber tires.
I'd love to know more details of the old "Beast" and it's soon to be put into service replacement, just from a purely automotive viewpoint. But I realize that's detail we'll likely never know.