I got lucky when I found mine in an old junk yard about 13 - 14 years ago. There is a section of the firewall that you will need as well. Once you look at that area in the firewall, it will be obvious where to cut the spot welds and pull the piece out.
The rear part of the High Hump is a direct bolt in, but the front needs the matching piece that is welded onto the firewall.
The previous owner had swapped out the 3 Speed for the SM420 4 Speed, but did not change the tranny tunnel. They just bent a piece of sheet tin over the area and screwed it down. Ugly solution! I had to fix that.