World Products makes a variety of aftermarket cylinder heads. Windsor Jrs have 180cc runners with 1.94/1.6 valves, and the Windsor Seniors have 200cc intake runners with 2.02/1.60 valves. Both are available in either cast iron or aluminum. They are available in 58 and 64 cc chambers. The only way to tell which you have with the engine in the car is to read the stamped part number off the end of the head.I guess I've never heard the terms "windsor jr" or "windsor sr". Enlighten me please!