I had to use a goodmark rear quarter to do a lower quarter panel patch on my 67 Cuda and the panel had it's pros and cons.
I found the goodmark packaging to be really bad. The quarter looked like it was laying flat and someone came and just stomped right in the middle of it over the wheel well. Luckily I only needed it for the lower quarter patch so I didn't even want to deal with making a fuss about it but it would have been absolutely useless if I needed to do the whole quarter.
The panel was plenty thick and fit pretty well in general as far as the outer part of the body went. Had a couple of problem areas. The body line that curves around the wheel well wasn't nearly as pronounced as the factory and didn't go as far down the panel as the factor body line did.
Also the panel had a lot of excess metal around the wheel well and on the bottom lip where it welds to the bottom of the trunk extension. Probably an extra 3/4" all the way around. I had to cut it off all the way around and it took a decent amount of extra time to get it all looking even. I have a feeling AMD wouldn't have had this problem and would have just mated up and that would have been the end of it. Unfortunately they are no longer making 67 Barracuda patch panels at the moment.