I've been told a JDM MP1A out of a '94+ Accord auto tranny will replace a '90-93 Accord MXPA or APX4 tranny. Has anyone done this? Are there any things to watch for besides using the flex plate and torque converter that come with the MP1A? Will the existing TCU work?

 

Yes, it will bolt on. and work.

 

Everything will work fine.
The two main things to look out for are that the seals for the axles on the differential are not damaged, and that the cooler hard lines for the transmission are not bent/kinked. I had to reuse the existing cooler lines from the car as the import trans lines had been damaged, you will need four new crush washers from Honda. These need to be changed while the transmission is out of the car.