Well here's the thing - and this applies to most reproduction stuff - dies for any metal part are not a single unit but multiple dies. There will be one to stamp the initial flat shape from the sheet, another to stamp the basic shape, another to bend flanges, and so on. A minimum of three dies and possibly six or more depending on the complexity. These dies are LARGE and heavy and extremely expensive.

So having said that, its extremely unlikely that there is more than one set of dies in existence for most repro parts. The exception to this rule would be in the case of Sherman's, who has been stamping out mediocre repro parts for decades. But I strongly suspect that both the Goodmark and AMD stuff comes out of the same dies. HOWEVER, the difference is in the gauge of the metal, AMD uses 18ga as was used on original parts and Goodmark uses metal that is 30% thinner. This applies to body panels. Grills are already thin so they're likely one and the same.

So in the case of grills it boils down to the finish. Are they finished (plated and painted) by the same outfit or not? Do they each have a different spec for the shade of argent (it would appear so).

So the bottom line here is that the fit of either should be the same. The only differentiating factor being the finish.