Need help with measurements for case modding

Sarofendor

Commendable
Nov 25, 2016
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0
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So I have recently come upon some money and I am going to upgrade my PC. I will buy a new motherboard and a new CPU cooler with the goal of being able to SLI in the future and being able to overclock. My relevant PC specs are as follows:
i5 6600K
Asus B150M Pro Gaming motherboard
EVGA GTX 1070 Hybrid Gaming
Corsair Air 240 Case
Cooler Master Geminii M4

Now what I am planning to do is buy the Matx ROG STRIX Z270G Gaming motherboard and also buy a Corsair H80i liquid cooler. My question is what are the dimensions of the CPU block on the Corsair H80i cooler? I need to know this because I want to install the radiator in the rear chamber of the case and I need to know whether I can fit the block through the cable management grommets or whether I have to cut the case to fit it through. My other question is if I change solely the motherboard, will I have to reinstall Windows 10?

I know it is kind of a big ask as I have not been able to find the measurements myself and I am very grateful for any responses.