It's just a slightly odd shape. Shit, you people are acting like it's something out of this world... For someone experienced with metal bending and welding, and with a chassis, or at least the rear half cut to be used as a model, it shouldn't be that hard. Obviously it will have square edges and might be a little larger or smaller, but as long as the mounting points, the pump base and breathers are the same, it should be all good. Shit, if I had to I probably would give it a try, except I would make it out of steel since Im not good with aluminum.
Check this one out
for the f-body, a not so simple shape, and they sell for $600
here's a site with more pictures:
https://www.behindbarsracecars.com/C.../bbrcc9802.htm
No wonder people out there don't get shit done, they set themselves a lot of barriers...