Upgrade your MKII pump with a 304 stainless steel replacement head. Stainless steel is more durable if you are attaching ball valves. Very occasionally the threads on the plastic head that comes standard on the MKII can break if you are using hard to close ball valves that apply a lot of torque. Stainless steel is very robust and will not break, is food grade, and well... stainless.
Before you snag the stainless center-inlet head, also consider the stainless inline tri-clamp head.
Kegland Part Number: KL03865