Have used Goodmark and non-goodmark panels ----all from Tiwan. Goodmark tells me they have a higher standard of quality, fit, thickness, finish thus their "certification" from GM. In reality, if they use original GM stamping presses, these must be well worn as their quality has never shown to be equal to NOS. That said, we sometimes get ticked at fit of a new panel, door, tailgate from Tiwan when in fact we have a : bed out of square, cab twisted, front rad support cocked etc. If you bought a full set of NOS sheetmetal, you would still need tweeking to get things to line up perfect thus the gigs that GM used at the manufacturing plants to line up assemblies like the doghouse etc. Most of the dealers are handling the best sheetmetal they can buy for us with weight and thickness pretty close to NOS. In reality it's hard to justify paying 2-3 times more $$$ for NOS if you can even find it, for a nice driver. Have just done inner, outer rockers and cab corners on a beautiful 71. Not one piece fit to the original that was removed. Have yet to find one set of outer rockers that was not 1/4 inch too short. So in summary, will make do with what I can get, ***** about it, then go hide in the barn tinkering before my love muffin gets me involved in one of her projects that I hate~~~~. Now if everything fit perfect I would have little excuse to hang out in the barn and have fun~~perhaps a small price to pay for "guy freedom"!!!!!!!!!!!!