I'm the wrong person to ask.
Engine = Ford 5.0L with EFI
gearbox = NP435 (first gear = 4.9:1, yours about 3.6:1)
Transfercase = Series high ratio
Diffs = 4.75:1
The engine has more torque coming off idle than the stock 2.25L does at peak and my first gear ratio is a lot lower then the LR gearboxes.
On the other hand with 33.3 inch dia tyres the engine turns under 2600 RPM at 65 MPH
My guess is your best bet for driving happiness is a stock Series transfercase and a Roverdrive.