Need help from someone who really knows Polaris engine specs

[yz400ex]

I am in the process of building a 2012 Polaris Rush 600 engine. I am in need of 2 cylinders and a cylinder head. I have been cross referencing part #'s from IQ CFI 600's and Pro ride Rush 600's and they are different. The bore is the same on the cylinders, but I dont know what the difference is?? Port timing? Stroke is the same, right? Anything else? Can the IQ CFI cylinders be used on the Rush bottom end?

What about the head? The cover is the same part # till 2013, but the head is a different part #. What is the difference here?? Compression? Will the CFI head work for me?

I am referencing the CFI 4 motors. Not the CFI 2. Can anyone help me out??