looking for dark tires for front

Have a 1300 r with stock wheels 17" looking at 150 80 17 's  .. I'm not a Bridgestone fan ,but the BT 45 seems to be a favorite.
What is the real difference between the 150 70 17 and the 140 80 17 it's going on the front. Will it alter the speedo , change the ride??

The two numbers that you gave shouldn't alter the speedO...

We  are using Bridgestone Battle wing rears on the fronts of our Valks ... 150 70R 17... OEM (150 80R 17)
A very small change  in the speedo.. No biggy... Getting great wear from them so far 7K and NO wear .......

here is a front tire in that size http://www.motorcycle-superstore.com/15017/i/avon-av71-cobra-front-tire im running the avon rr am 21 on my v star 1300,dunno bout were yet but made the front almost as smooooth as the goodear tt did for the rear and very sticky

Here is the answer to all your fitment questions;
https://www.tacomaworld.com/tirecalc?tires=170-70r16-195-60r16