Many years back, I bought a Dutchman panel for a B body from Sherman but I'm not sure that they actually stamp them. It fit well though whatever the brand was.
On my current E body project, I have been buying whatever is cheapest (usually good mark) and I've had no complaints. Fit Has been quite good. Be warned though that I've found slight cosmetic difference in Goodmark from original but so far I'm working on areas that are not noticeable so hasn't been a deal breaker for me.
I used an AMD upper cowl on a friends car and it fit like a glove. Appearance was dead on too. My plan is to use AMD on all exterior stuff like fenders and quarters but use other brands to save a couple dollars on areas that is not as critical on appearance.
Lastly, I always use a gauge to check metal thickness on replacement panels to compare against original thicknesses and so far, I have always found the replacement parts to be the same thickness as originals. I do this out of curiosity since there are some folks who complain about replacements being thinner.
