I have a 1971 coupe that im putting 17x8 inch rims on. What is the best tire size for my application?

Hi Mike, I have 17X8 Torque Thrust II wheels on my 74 and put Kumho 255/55R17 tires all the way around.  The diameter is just a little more than the stock tires and look good on the car.  The only thing I advise is you might want to put a little narrower tire on the front as mine rubs slightly on hard turns sometimes.  You might try 245's or less.  Good luck and be sure to post some pix when you get them on.