During the manufacturing process, the dies used to stamp sheetmetal will get worn. this is especially problematic when you have a body panel with crisp, hard lines and edges. So, the problem is tha the lines may be "soft" or not straight. Many guys have reported that some of the reproduction pieces, like the quarter skins for the Challengers, are not suitable for use. Instead, they cut the quarter skins above and below the belt line and use only what they need. The Goodmark pieces should not have the problem. I think that ANY panel you get is going to need massaging to make fit properly. This is not necessarily the fault of the panel, but is due to the fact that the car is 30+ years old and these cars weren't put together well to begin with. The margins and seams on these cars were screwy to begin with. Bottom line is that if you NEED a new quarter, go with the Goodmark units as intact quarters off of a salvage car is impossible to find and NOS pieces are overpriced and no better than the Goodmark pieces. If you can salvage what you have with patch panels, you can probably get as good a result without as much work (if you are paying someone to do this, just get the Goodmark piece).
As for the decklids, they are known to be problematic in terms of fit and strength. Apparently, they are rather flimsy. Again, ANY piece is going to take work to get fitted properly. Go get 5 good decklids off of different Challengers and each one will fit differently on your car!
OK....I'm going to get on the soapbox for the moment, and this isn't directed at anyone in particular. A lot of guys complain about the "poor fit" of replacement sheetmetal. This is just silly. I took close note of 5 or so VERY nicely done E-bodies at the Garlits show. We're talking $100K+ cars. Do you know that each car had variances in the overhang of the quarters relative to the tail panel? In fact, on any given car, there were differences from side to side. I KNOW that some of these examples were original! Also, anyone who has completely dissasembled an E-body or any other Mopar of the era KNOWS that these things were put together with a big hammer! Thus, there is no way in hell that any one body panel will fit all cars because all cars were different from the factory and have experienced different things over the past 30+ years! Now, to say that some of the stampings are thin, flimsy, have soft lines, or stuff like that is fair, but NO part is going to just "bolt on" without some work.
