I've owned 3 Turbo/Targa/R154's and only 1 Turbo/HT/R154 so I vote for the Turbo/HT's being rare.
From my experience (common - rare): Sunroof/moonroof, Turbo/HT/R154, NA/Targa, Turbo/HT/Auto, Turbo/Targa/Auto, Turbo/Targa/R154, NA/HT. I realize I'm probably wrong compared to the actual...