I have a 1985 Trans am WS6 with I believe the 16x8? Inch wheels stock. What tire can I fit out back? Looking for badass, mean stance. Would it be noticeable if I had a 265 out back and a 245 up front or a 255? Or should I go with a square stance? Or maybe 245's all the way around for better donuts.

245-50-16 rear and 225-55-16 in front. That gives you same height but a touch wider in the rear.

I put on the BFG Comp TA 245/50/16 all around on my 85 WS6. You can use 255/50/16, but the tire will look a little balloonish..so to speak.

While there are some 255-50-16 tires on the market, the 245-50-16 or 225-55-16 are better choices due to tire selection.

If you want stance, 16" is never going to do it - you need 17" or larger...