Download these:
http://aminet.net/package/util/boot/BlizKickhttp://aminet.net/package/util/boot/LoadModuleand unpack them to RAM.
Use romupdatesplit to extract the scsi.device for your Amiga model from the AmigaOS ROM Update file of OS 3.9. Read the readme file to find out which one you need to use. Do not use the wrong one or your Amiga won't boot any more.
Copy scsi.device to Devs and LoadModule to C of your 3.1 partition. Add this as the very first line to s/startup-sequence:
loadmodule devs:scsi.device