if Diesel is an option, do look into 1KD and its numbers of torque, power n mpg. A bit of tuning can make it more powerful. If 1KZ is being replaced, it might be a bolt on or close to bolt on option. It has the history for injectors/nozzles issue but thats pretty late in life.
Not sure if our mechanics can reliably work out Petrol conversions other than 5vz, 1uz.
Any ideas on 2uz or 3uz?