Went through a couple sets myself. IME, the fit is terrible. The repops I used were obviously not bent the same as my originals. I made them fit, but it took some serious work, and they still don't equate to originals.
Ditto for the headlight surrounds. Bend and radii details are sloppy and incorrect. Surface finish is rough and uneven.
A popular vendor has admitted to me that "only one company" is stamping these particular parts, and that "the fit and finish is not that good at this time". That was in mid 2012.
The landscape for 66 model reproduction bright work and grille trim remains bleak, at least as of late 2012, when I ordered my last parts of this type.
P.S. The 66 SS grille I bought was from a well known vendor. It was widely advertised and recommended as a "premium part". While cosmetically acceptable, it was plagued with serious problems, including most especially incorrect metallurgy. The Aluminum selected by the repop mfg. was a much softer alloy than OEM. I did a Rockwell on both - this is not a guess on my part. The OEM part appears to be A93004-H34 alloy. The repop is A93003-H14. That's 33-50% softer...no doubt to save a nickel. Result is that the repop grill is so soft it cannot tolerate even the slightest bump, push, impact or even "lean up against it" without seriously deforming. Basically, it is an imitation grille - incapable of actually performing its primary function. :-/