To answer a few questions about the Defender 90, the tires that I am running are
265/75R16 they are stock tires. The vehicle runs the best around 1800 rpm. Now after all the great input from our community, I am going to install a Banks Sidewinder turbo. This would be the cheapest and (for my application) the most logical thing to try first. What makes this vehicle a bit different that it's America compadres is that this vehicle doesn't have any components that are aerodynamic ,it is as if you are pushing a large chalkboard down the highway. The turbo should allow me to push through 5th gear with the overdrive engaged, I don't need much more power, also, it is claimed that I should see a increase in fuel economy.

My challenge will be in installing the turbo. Can the turbo be installed underneath the vehicle? Is it loud? In general, does a turbo increase or decrease the life of the motor? If there proof in the claim by a respondent in this thread, that a overdrive decrease the life of the motor and if so, how?

Thanks! -Madrugador