Will ecu from a standard work in automatic?

 

No, and yes.

Which year, which standard, which automatic?

For a 1996, no way if you want the car to move.

For any other year, you'll lose the overdrive (if a 4 speed) and the torque converter lockup (on all the autos, 3 and 4 speed), but those can be supplied by other means.

Any particular reason why you want to swap ECUs but not put the right one back in?

RwP