Bob,
When I bought my dummy GP9 it did not come with the "Power Transfer Gear Assembly" and coasted quite well. Here's a link to the 3-rail trucks and gear assy:
http://www.atlaso.com/partspdf...truck%20complete.pdf
I can't imagine Atlas putting the PTGA in the F3 dummy because of what you have stated (and cost).
I bought the PTGA and equipped my GP9 with MTH motors and mounts and now I have a powered, nice running Geep. The MTH motors and worm gears(correct term?) fit like a glove!
If the engine you have is one you want to use as a dummy I would check it and remove the PTGA if necessary.