Depends on a lot of things.
If the HD is IDE then Norton Ghost will duplicate it. You can install the replacement drive in the SCO system as a slave on the primary, or as the master on the secondary IDE controller, boot from a DOS/WIN95/WIN98 floppy, and run Norton Ghost to duplicate the drive.
Presumably the system has a CD which you could replace with a DVD Writer and install Microlite Edge (Home of Microlite BackupEDGE / RecoverEDGE).
This software will create a backup of the entire HD that can be restored to any system with a similar disk controller.
You will need to upgrade to 5.0.6 with all patches installed to upgrade the cpu to a P4