Just checking Joe's catalog and the front for the '36 is listed as zinc plate and the rear as stainless steel. The rear shown is also a little different than the one on my car. On a close inspection, the one on my car looks to be hand made from stainless steel sheet metal.
That would fit with other things I've found that were obviously not Ford parts. The car spent a lot of years in the collection of Dee Howard, who had extensive aircraft fabrication shops in San Antonio. The whole exhaust system is made of stainless steel TIG welded tubing. The fuel lines are also aircraft tubing and AN fittings.
I think I'll order the catalog parts.