HY!
i have searched in the www and found 3 types of Engine in the RX300/Harrier
ACU10
ACU15
MCU10
MCU15
SXU10
SXU15
ACU= 2AZFE: 2400CC 16VALVE DOHC EFI
MCU=1MZFE: 3000CC 24-VALVE DOHC EFI
SXU= 5SFE: 2200CC 16-VALVE DOHC EFI
xxx10= FWD
xxx15= AWD
here a interior of a 2,2L Harrier.
on toyo-diy are the transmissions-partnumber only different on the last 2 digits. and looks like the same.
with a wiring diagramm was easer to find a solution, but i think, its different transmissions-ECU in the cars. to modify, i think we need the gauge cluster, shift lever, steering wheel and may cables and bits and pieces.
3 Gears + O/D is ok without shift-padels, a 5-gear transmission was better with padels. I have see in the GS430 S16 no shift padels

but he have 5 gears and enough power

i hear, its no good for the 5-gear transmission