Dell Precision T7810, looking for front and rear case fan sizes.

As it says on the title, I would like to add a rear case fan, and replace the front fans.

For some elaboration, I’ve been doing my homework about upgrading a T7810 I saved from the dump two years ago, and I want to upgrade it in the first place for my girlfriend whose current computer cannot be upgraded since she wants to play games with me, and building an entirely new computer from scratch would cost more than souping up this Dell I got for free. 

The current computer works fine, the power supply is some 800 watt one, so the graphics card I’m eyeing for it would work with an OEM dual 8 pin cable, and the processor upgrade I want would be compatible with it (Xeon E5-v3). I would be aware that a case with poor airflow would not be kind to a higher clocked processor, and a proper graphics card. So I’ve been looking into a 2011v3 Noctua heatsink for it, and from what I saw from someone else doing it on the same model of computer, it’d work with a tiny bit of finagling. 

However, again, I am stuck at a small conundrum, I would to replace the front fans with better Noctua ones but I do not know their size but both google and duckduckgo are being uncooperative with me asking this, and as well I would like to have a rear exhaust fan to help pull out air from the case but I cannot find any measurements on what it is. I do not have any good measuring tools. 

Thanks.