They use another brand (he wouldn't tell me). So tracking down a Teac FD-235HF and trying some voodoo magic work on the pins won't help.
Originally they were doing the mod with a Teac drive, but these are hard to get now so maybe they found another drive to modify...
If I would have more time I would try to find out things myself, because we have the full specs of the disk drive of the Emulator II now, including RPM, data transfer rate, pin signals, etc. So it can't be that difficult - the 3.5 drive just needs sufficient jumpers or documented schematics to modify it according to these EII specs.
Anyway it will be easier to wait for the information from your friend and from Peter's tech.
If that's not going to be useful, I will have a look to some 3.5 drives and do some experiments.