Does anyone know the correct speedo gear for 265/75R16 tires?

Which gear ratio do you have in your differentials?
 
Which gear ratio do you have in your differentials?

With that disparity in true mph; I would say 3.07s.

The tire you installed is approximately 31.65" and the closest you will get to calibrate the speedo with 3.07s would be a 26 tooth gear.

jeep-speedometer-gear-chart-26.png
 
8 mph at what speed? The variance will always be a percentage, not a fixed number. For example before I fixed my speedo it was 13% slower than actual. So at 15 mph indicated it was about 17 mph actual or 2 mph off. At 70 mph indicated it was about 79 mph actual or 9 mph off.
 
With that disparity in true mph; I would say 3.07s.

The tire you installed is approximately 31.65" and the closest you will get to calibrate the speedo with 3.07s would be a 26 tooth gear.

View attachment 190256
I'm assuming the color coordination is more than just different colors here? Maybe Green is the ideal place you'd want to be? In my case I know I'm running 33's and sitting with 3.73 and my gear would be a 30 tooth gear. But the ideal would be for me to upgrade my diffs to 4.88 and run a 39 tooth gear because it's green. Am I reaching here?
 
I'm assuming the color coordination is more than just different colors here? Maybe Green is the ideal place you'd want to be? In my case I know I'm running 33's and sitting with 3.73 and my gear would be a 30 tooth gear. But the ideal would be for me to upgrade my diffs to 4.88 and run a 39 tooth gear because it's green. Am I reaching here?
Yes I think you are reaching but if you want to look at it that way, I think what you want is to be somewhere in the middle of the range which should give the best balance of on-road and off-road performance. For you, 4.10s would put you directly in the middle with 33s.

I am running 31s with 3.07 which puts me at the limit of what the speedo teeth support (they don't make a 25 which may or may not tell you anything). But I interpret this as I should be regearing to 3.55 or to get back to the middle.

Of course, transmission matters so there is another chart available to get recommended gearing based on engine, transmission and axle ratio.