I've always understood that T tops are two piece tops where a center piece runs down the middle, ie: C3 vettes, Firebirds, Camaros, MR2s, Pulsars etc etc.
Targa tops are where there's 1 removeable piece leaving no frame member in the roof. Ala C5 vette, Mk IV Supra, Porsche 911s etc
Our cars are unibody and the top is a structural member that ads gobs of stiffness to our cars, when you remove it you'd have to add adequate bracing. Wonder why? Open both your doors, back up and take a look at the car from the side, now pretend the top isn't there.... There ain't much left...
All that said it looks badass and it'd be so sweet to be able to pull the whole top off. Mind you, they almost always leak... and squeek...
I've heard rumours and seen ads picturing a 1G targa top, the rumours say it was european market only. If you could hook up with a real factory targa top 1G you'd be my hero, especially if you sold it to me