Gear Ratios…!! HELP

[DiscoQ8]

Hi everyone,
I have a small problem and need some help with my Disco1 (98), I‘ve changed my tire size from 245-70-R/16 to 265-75-R/16, which made my top speed 130 kph..?
For your information my truck has a Manual Transmission with a Range Rover 4.6L Engine…!!
So, I think I need to change my Gear Ratios…!!
But what is the Ratio need that will improve my top speed and my truck OFF-ROAD Performance..?
Thanks in advance.

[CliftonRover]

I am surprised you need to change the gears, but the most common swap is from the rover 3.54:1 to the 4.10:1 ratio. you can get them from great basin rovers or Rover Tracks