SCSI ID Selection at boot

[SDUBjed]

I cannot get my powerbook 540c (OS 7.5.5) to boot from a specific SCSI ID even when trying to manually select at boot (Command-Option-Shift-Delete-#).  

I have two different system drives on the same scsi chain, but it will always boot from the drive with the higher SCSI ID.

If I manually change the drive IDs it will boot correctly, but this is inconvenient to accomplish as I use the drive on another machine that would need to be switched back every time.

Can I manually set the boot SCSI ID in software?

Thanks!