A decade ago a friend put a Pintara 4 speed auto into a 1200 ute for somebody. they put a 120Y floor in, & I think they used the O/Drive switch to lock up the transmission to get 4th gear. The switch was wired so when it was turned on, the convertor locked up,instead of the usual way where the convertor unlocks.This is because there's not a passageway for the fluid to do the usual lockup. The only problem is the friend who did the work passed away not long after & I never got on with the owner of the car. The only name I knew the owner by was Gadget, he only had 1 arm, which is why he wanted an auto. the builder was Ron Johnson from Ingleburn Steering. So it is possible & I have considered doing a Sunny with a 4 speed auto myself.