As far as I know they are manufactured by Sherman and Dynacorn. I have no experience with the Sherman product but Mustang Monthly featured it in an install how-to a couple issues ago and seemed to like it. My local vendor just came back from a trip to Dynacorn's facility and really is impressed with the quality of their product. It seems to be a heavier gauge metal, much closer to original than any I have seen and the fit on his customer's cars is really nice (I have seen their doors, fenders, and hood as well as their 65-66 full trunk floor) Don't know if that helps, thought I'd throw in my .02 cents' worth. My vendor tells me that the folks at Dynacorn have a ton or original cars and parts at their facility and they are reverse-engineering each piece to exacting detail. Seems like a dedicated crew to me.
I have heard the Dynacorn pan is a much crisper stamping. Look in the parts for sale section here. They were being sold for $459 + shipping. When I get one I'll post some pics of the install.My understanding is Sherman pan is heavier than OEM floor, thus, I'm guessing the inability for a crisp stamping.
We have a local dealer who sells only Dynocom sheet metal parts. He swears by it and will be replacing most of the sheet metal on his 65 fastback which will remain unpainted to advertise Dynocom products. I have seen most of their products including the floorpans, front frame assemblies and convertible only parts. Not sure how well they fit, but the feedback has been good. Checkout the link.