Try Defender 1.411 transfer case
On my Disco V8 have fitted Defender high transfer case ratios and 245/7516 Coopers. Makes a world of difference, speedo is within a bee's wick of spoton and it gets up and goes. Lower 1st gear, also 300 more rpm at 100km/hr means the V8 is able to get up more where the torque is. 2125rpm standard transfer case ratio for 100km/hr is no-go zone, IMHO. I can now overtake in 5th with reasonable acceleration. BUT economy is better, as I guess the motor is spinning freely with less loading up.