Just so you know, "early A body cars" are '66 and earlier. '67 and later (like your '68) had redesigned hinges that eliminated the earlier design's torsion rods. Neither was a bad design. As far as it being a "common problem", it's more of an issue because of these girls being 50-60 years old with a sketchy maintenance history rather than a design flaw. Let's face it, this will probably be the first time in all those years that your hinges have ever been lubricated!
