The most significant improvement for 1964 was the change from the dogleg windshield to the conventional curved type. It provided easier entrance and exits for driver and passengers and looked much better too.
The 230 and 292 six cylinder engines continued as the standard engines for all 2 wheel drives and beginning in 1964 for all 4 wheel drive pickups also. The 235.5 and 261 sixes were dropped. The 283 cubic inch V-8 remained optional for all C/K pickups. The 1964 models continued through 1966 without any changes worth noting.