You best bet is to look for parts from a salvage yard in dry country, or look around for enough pieces from rusted out bodies that you can piece a new part together.
The kind of fabrication you are looking for is old time body work with shot bags, planishing hammers, welding, and a dozen or so other skills. The original part was manufactured by drop hammering in a humongous press - you won't want to buy the dies, let alone the press.
There are probably other places on the net to look for info, but if you go to Kent White's site, you can get all the info and tools you need to make a new part -
[url]http://www.tinmantech.com/html/kent_white.html[/url]
Unless you have transferable skills, don't expect to equal Kent's work right away - he's been at it for decades. He also knows what he's talking about [He taught me how to weld aluminum with oxy/actelyne.]