Assuming that both machines had the same host adapter:

Change the SCSI address on the second hd so that is different from the boot disk. Check SCSI termination. Add a write protect jumper if this is available.

Boot the machine with both disks installed.
Run 'mkdev hd'
Enter the info for the second drive, rebuild the kernel, and reboot.
Run 'mkdev hd' again, entering the same info as before.
This time fdisk and divvy will be run.
You should not have to change anything in fdisk.
Be EXTREMELY careful in divvy. You can erase everything in seconds!
Do not change any FS types, start or end addresses, or create any new file systems.
Use the 'n' option to rename the file systems so that they do not conflict with the names on the primary drive. (eg change root to oldroot, u to oldu, etc).

Run scoadmin->filesystems, and mount the filesystems that you require.