Wow! is all I can say. It's amazing what people do to these great machines.
Best advice would be is to marry up a new board that when in place replicates the full height of what it is supposed to be. There will be gaps because of the bad hand saw cut that was made but can be easily filled with bondo. Finish by sanding and then either do your best painting or buy the decals and if the front does not match the sides,then also do the side decals. Or just live with the front being a different color than the sides. Not much more you can do imho.