Man, sounds like a nightmare indeed. I guess I would try disconnecting the driveshafts and see if the output flanges spin in gear, from internal friction or whatever. It sounds like you know your way around a wrench, did you confirm the selector on the side of the trans is moving into the correct location when you move the PRNDL? Did you make sure the torque converter was fully seated into the bell-housing before mating it up to the engine? One of the files in Extinct's link addresses this. I'm not familiar with the output shaft speed sensor, where does it live? I can't imagine that would prevent the vehicle from moving at all, maybe shift goofy and/or throw codes, but no motion at all being the result of an electronic sensor seems extreme.

 

I guess it comes down to whether it is mechanical or electronic. I'm leaning electronic since you have done so much work on the mechanical side. I'll assume your installation of the transmissions was sound because I have no way to diagnose that.

For that reason, I'd replace the ABS ECU and perhaps the trans ECU.

 

TCU is a great suggestion. Have you swapped it? Do you have a spare? SLABS too if you've got one.