Welcome,,, hopefully some of the Nova dudes will step up and help.... Typically with a stock car in that era you will be able to get at least a 255 up front and a 275 out back with minimal modification. However, this all depends on the rim selection and how low your car is. I personally have never selected tires for a Nova, but have modified a 72 Nova to get 315's on all for corners.

if you don't get an answer from one of the nova owners, then try taking your car to a tire dealer for some test fits.

Good luck.