It's not difficult, but you'd lose a lot of film resolution, because you'd either be (1) matting the sides to make it fit a flat screen, which would reduce the size of the frame by 50%, or (2) matting the sides to fit a scope screen, with pretty much the same result. In other words, grainy as hell.
BTW, Bubba Ho-Tep was a lot of fun. Apparently, since Coscarelli decided to distribute the film himself, there's only 6 or 7 prints out there. I consider myself very lucky, especially since I only paid $6.