Great project. I've been working on the same design for some time when I ran across your post. I'm picking up an Insight this week for the conversion ('01). I have the prius trans and inverter and will be starting the design for the controller to drive the inverter in the next few weeks. The prius dose use a reluctance position encoder for phase timing unlike the honda which uses hall sensors. I like your idea of synchronizing the motors to use one input control signal. It greatly simplifies the controller design. I'd like to use the prius ECU but with no information on it I think that a custom design might be easier. One possibility for an off the shelf solution is the Galil (www.galilmc.com) controller. I've used several in CNC projects and they work very well. A three axis version is available and would also provide all the commutation as well as the PID functions for tuning. (you can combine axis to provide three phase drive for ac motors). Just need to work out the interface to the prius inverter. If their is any thing I can help with on your project count me in.