Cool modification! To my knowledge, at the moment there even isn't a white T-top Greenlight Collectibles GTA available other than the Indy500 Pacecar version.
Found some time ago information about the upcoming versions of the Greenlight Trans-Am:
T-top & hardtop versions, new colours (White & maroon metallic), V6 Turbo Trans-Am (TTA)
Also some very limited gold & chrome collector's editions of these models
Seems these new versions will be released in March or April next year:
http://www.diecastmusclecars.com/transam.htm" onclick="window.open(this.href);return false;
Hopefully they will make the '82 Black & Gold Trans-Am, Michael Long's car as well at some point

I'd also like to see 3rd gen Camaro made by Greenlight.