I never actually owned an Imagewriter II, just an original model that came with a Mac 512k. When we had an Apple IIc, we used a Grappler C adapter to connect a parallel printer to the serial port and it had the option to emulate an Imagewriter.

Anyway, I think the later units used a simplified power supply. They certainly were lighter and less tank like. If you are interested in information on the expansion connector, I have the technical reference for this printer and for the LQ. Oddly the IW II manual has close to zero hardware information, while the LQ book details how to make an expansion card.