The vinyl top looks fairly recent, so most likely this car is undergoing one of those very slow restorations and being used as a driver in the meantime. Perhaps it will become a trailer queen once the project is done, but for now it shares the road with Tauruses and Sentras.
The GT option package got you a 289 V8, disc brakes (which were still quite exotic for a Detroit car at the time), fog lights, and stripes. The most powerful engine option was a 4-barrel 289 with 10:1 compression, good for 271 horsepower. The 2,690-pound '65 Nova could be had with a 300-horse 327, giving the Chevy a slightly better power-to-weight ratio than the 2,465-pound Mustang.