Hi Ron:
Before I got too involved with MTH AEM7s, I explored installing PS3 in an Atlas AEM7. Physically, it isn't possible; the Pittman is just too big. However, you could get around that issue by installing it in a gutted coach with a permanent tether.
The bigger issue is the electrical specs on the Pittman 9233 series motor, (datasheet). It runs on 24VDC and stalls at 6A. I tend to run long trains, and that motor will draw between 1 and ~3A depending on the load and grade. My MTH units hardly ever draw over 1A. Even without the current draw, the voltage difference and tach wheel mismatch makes it quite a challenging build.
I also lament the lack of proper control with Atlas AEM7s, as they are awesome units. The best idea I have to is to install an ERR board somewhere or just enjoy them conventionally. I am sure some enterprising soul could make PS3 work, but I do not feel it is worth the time and subsequent hassle to try.
