Hey Robert, I work for AMD so I can shed some light. Generally, the "premium" panels were developed in recent years and feature newer, crisper tooling. The non-premium panels are usually what we refer to as "crash parts", or what's been available to bodyshops for the last 30+ years as cheap replacement parts. The crash parts are generally lighter gauge metal and more universal in hole placement/features so they'd cover more years.
If you look at our site, you'll notice we don't play the premium or non-premium game. If it's branded AMD, we developed it here in house in Georgia and it's a premium piece that matches OE as closely as possible. Contours, thickness, bodylines, holes, mounting points, etc. If it's an "X-Brand', then that's not something we had anything to do with the development of, we just source it from elsewhere, but we've evaluated it and decided it's a good piece. For squarebody trucks, we've just about developed everything you'd need ourselves.
That said, alot of people don't realize how much variation there was in original pieces. Contrary to Rick's statement, original pieces are not all the same and did not come from the same place. There were several foundries/stamping plants for the OE's and we have disassembled and evaluated enough original stuff to positively say, there's as much variation in original sheetmetal as there is aftermarket. I've personally fitted so many OE squarebody doors on OE cabs and seen how the same door fits 5 different cabs 5 different ways.
I say all that just so you're aware, you may have more adjustment to be done on a new panel that what you expect, because your truck may vary from the ones we developed our stuff off of. A good example is hoods. Lots of people buy a hood, slap it on the truck and are unhappy with the gaps. What they don't realize is, in many cases the fenders, hinges, and core support need to be loosened and adjusted along with the hood. Sometimes that even moves into adjusting the doors. Just like building a fresh drivetrain, all the pieces have to be adjusted to play nicely together.
Do your research and buy from whoever you like the best, I'm on this forum personally, not for AMD. But I can tell you we're a small company of legit car and truck guys and take pride in our work. I wouldn't come to bat for us if I didn't like and use our products personally.
