So your 1983-1993 Mustang Convertible suffers from the floppy 1/4 window syndrome. The cause of sloppy convertible quarter windows is not always guide bushings. More often than not, it is cause by a broken 1/4 Window Guide Rod Mount.
Form the factory, 83-93 Mustang Convertibles were equipped with a less than optimal plastic Quarter Window Guide Rod Lower Mount. They are very prone to break & cause the "floppyness" you experience. To permanently remedy the issue, we produced these billet aluminum 1/4 Windw Guide Rod Mounts!
Our Billet Guide Rod Mount is the only one of its kind on the market & is exclusive to us. It includes all new attaching hardware for ease of installation. You only want to replace these once as they are a pain to get to, so make sure you go for the permanent solution!