Brian,
The convertibles did come with stock additional supports. The stock ones are tubular I believe. The export braces you are seeing in the catalogs are like the ones that came stock on the Shelby models. In essence it is a one piece unit that is stronger than the stock brace (that came on the coupe models). I'm not familiar with the early ragtops so I don't know if the stock setup is fine on yours or if you can even swap it for the 1 piece brace. Someone else here can tell you for sure.
Hope this helps a tad.
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66 Tahoe Turquoise Coupe
Laser Red 96GT Ragtop
Both are slow but easy on the eyes!