The 1983 Fox-body Mustang GLX convertible almost never happened the way people assume — Ford shipped brand-new coupes out to a contractor just to get the top cut off and a folding roof installed. Add a four-barrel carb that boosted the 5.0 V8 by nearly fifty horsepower, and you have got a genuinely underappreciated turning point in Mustang history hiding behind a badge nobody talks about.