Sorry, Mac128, but the only way that it will work is with the original installation disk. The original Mac OS did not realistically support "external drivers". The INIT interface existed but was poorly documented, so manufacturers of serial hard disks inserted the driver code straight into the System file. Depending on the manufacturer, you received a new boot floppy or a disk that would patch an existing boot disk. Apple were continually making major changes to the Finder and System at this time, so version compatibility is a further problem.

As you've discovered, prior to SCSI, most third party disk manufacturers used generic MFM drives. Plus a serial or floppy port interface to connect to the Mac. I think that we must assume that all OEM interface boards are different and require individual drivers. But it is always possible that the design was shared by other manufacturers.

Mac128: Mail me privately for a copy of my notes about HD20 alternatives.