The 6265 would work well with your combo. Injectors would be fine as well.
I would also recommend our Air Cooled Dual Ball Bearing center cartridge, for the absolute quickest spool up available. This turbo is available with 3 compressor cover options.
E cover (3" in, 2" out)
S cover (4" in, 2.5" out)
SP cover. (4" in, 2.5" out with ported shroud)
For a street car, I would recommend the SP cover, for not only reliability but also for surge protection under partial throttle conditions.
I completely understand about your GTO. If it's low miles and in great condition, you're in good shape. Brazen Orange is one of the most highly sought after colors.
Hope this helps.
Patrick