Converting from a 6.2 to the best 6.5L Turbo Diesel for a Defender 90

[Madrugador]

I am a newbie to this forum and in need of a lot of help. I currently have a Land Rover Defender 90 with a GMC 6.2. It was installed not too long after I bought in 2005. For folks not to familiar with Land Rovers, their engines are inherently prone to problems. I have been super happy with this motor, but because of the gearing for the vehicle is for a high revving engine, at about 70mph it was at the maximum rpm output for the 6.2. So I added a overdrive and that helped the situation a bit better where I can go about 70mph and the engine doesn't sound like it is going to explode, but the RPMs at this speed is still a bit on the high side. Well the only thing left for me to do was to change the ring and pinion to a higher ratio and in doing so, the vehicle in general runs infinitely better, however the vehicle has trouble maintaining 5th gear with the overdrive engaged. The great thing is that the RPMs are in the optimum power range for the motor and best of all is the noise level is significantly reduced. In order to push through 5th gear with the overdrive engaged, I need more power.


I am new to the world of Diesels and the reason that I have a GMC 6.2 is that my mechanic thought that this engine would be a great match for this vehicle. It took him a little over a year and a half to install the engine in his spare time. Since it was a monster of a project for him and I would like to have quicker use of my vehicle upon installation, I am going to need a shop that can work on specialty projects or a shop that is familiar with the Defender 90. Now that a 6.2 is already installed, wouldn't a 6.5 or Cummins be easier to installed? There is alway the question of room? I am thinking that if a 6.5L can fit a Jeep then the 6.5L should fit a Defender, how can one know for sure? Are the new 6.5L motor like the P400 AM General more fuel efficient that 6.2 motor? Because there are counterfeit motors out there, I am going to need to know what reparable suppliers to purchase a motor from?

Any good tips would be greatly appreciated! Thank You for your time.
-Madrugador