The MAGTAPE command on p.6-55 of the Amiga OS DOS book states that this command "retensions, rewinds, or skips forward SCSI tapes.". By default, the MAGTAPE command uses SCSI device unit 4.
If you want more flexibility than this, consider obtaining the "TapeWormFS" file system that turns your tape drive into an AmigaDOS volume. There are updates to this file system on Aminet. I've got it, plus 2 Amiga 3070 SCSI tape drives, one with a fan that no longer works & needs replacing.
I've got the 3070 Installation guide booklet that describes how to change the SCSI unit on the DIP switch.
The unit is actually a Caliper CP150, electronically speaking, with them slapping Commodore's name on it.
Hope this info helps you.