Moto Guzzi 2015 V7 special

Hello everyone, new user here. I am wanting to switch out my speed and tachometer on my Guzzi, but am not sure if the ones I'm looking at will work with my ride. I'm being told by Dime City that I need to know the specific ratio of my bike, but I haven't been able to track that info down. The link below is to the speedometer I am looking at. Any help is appreciated.

http://www.dimecitycycles.com/2-5-inch-chrome-mini-speedometer-with-white-face-and-led-indicator-lights.html


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