Hello,
It's been years since I but a SCSI HDD into a Mac Classic but if I remember correctly the Mac always required the SCSI ID to be 6, you could therefore assume that the Drives are internally strapped as SCSI ID 6.
They should work on an A2091 Controller card with no problem.
If you can send the Manufacturer and Model Numbers of the Drives we might be able to provide more information.
Cheers
Shaf
