The rear heater might present some challenges.
And parking brake...
It's just a simple "box", anyone could bend one up at home with very minimal tools (maybe not Super neat bends, but functional). The trick is fitting it around what you want to keep and don't want to re-route. Parking brake ought to be easy enough to revert to the T-handle pull that was on my T100, and most people are doing away with the rear heater anyway (though removal of the coolant lines). Pre-99 also have a few switches there IIRC....
Then you get to think about integrating it with the forward console that houses the shifter and 4wd handle. As I think about this more, I suspect I'd use what was there as a "plug" for a fiberglass (or carbon fiber) mold. Add to the "plug" with foam/clay/playdoh/used bubble gum to get the shape you want and then tape it up (clear packing tape takes release agent well). About 3 layers would be enough for structural to pull the plug, then add whatever interior supports, cut the top and add a lip for the lid, etc... it'd fit the space perfectly, blend into whatever you wanted to leave behind, etc...
A good bit of work, but nothing outlandish. The other option is to get it into the computer as a 3d model, then make adjustments to size/shape as desired and "flatten" the pieces for cutting out of a sheet stock before folding up. This would be more robust (does it Need to be robust?), easier to scale up into mass production (I doubt there's THAT much market), etc...
Last option is to take something that's "close" and a cut-off wheel to make it fit. Add back with similar gauge steel, and just drill/rivet the patches/addition into place. More "Mad Max" looking.
I guess it all depends on what you're looking to get out of the change? One could fully customize with a specific light holder, holster clip, neatly arrange pen and pad holders, etc... if that was the desire. Shoot, design it right and you could "false bottom" a hidden lock-box into it should you want to break-bad.