Convert Engine on a Range Rover 1987 to Diesel

Hi,
I have a 1987 Auto Range Rover with a V8 engine and i would like to change the engine to a 300TDI, but with the diferences of power between this two engines i ask: Have any way to change this engine without change the gearbox ? Using A Flexplate or something else ? Any tips or experiences will be very helpefull
 
Best Regards