Almost a year later, and almost enough cash to buy the Lexus V8!
The engine compartment is ready and waiting..
Plenty of research later, I confirmed that decent Jeep engines are few and far between, and economically not a proposition. Having made the amazing discovery that the existing gearbox is actually a bolt-on to the 1UZ-FE Lexus V8 , this finally made my mind up.
The next decision was between the VVTi version and the non VVTi version.
Non VVti would mean no conversion necessary on the gearbox end at all. However, I eventually decided on the VVti for the sake of gaining a 5 speed automatic instead of the 4 speed gearbox, plus the fact that the VVTi puts out higher kilowatts, and is a more economical motor to run. Adapting of the existing transfer case to the 5 speed gearbox will be needed, but this is not difficult to overcome.
The old Jeep is still in great condition.