Hello Mark,
when you are ready with your machine up and running,
you could try to use on a real Nova 3 the tool I wrote to raw read/write
disks and tapes through the serial port.
You just need a PC (linux preferred) and Python installed (plus serial
port module).
Then you should be able to dump the disk to image for SIMH, and
eventually to write back an image to the disk.
Thanks
Andrea