As Paul said, assuming it is an external unit that was connected to a Smart Array, simply connecting it to another Smart Array should bring things back. 1997 era storage products that were Compaq branded were just dumb SCSI disk holders, with no array intelligence inside them. Thus it was likely cabled to a Smart Array PCI card. Based on the age of the boxes, I'm guessing a 2/P or 2/SL.

Writing a disk signature to each individual disk would likely cause damage, including possibly complete data loss. I can't remember exactly where on the disk the NT signature goes to say for sure though.

One world of advice. Try and make sure the Smart Array controller you plug these disks into has at least the same, if not newer firmware then the controller they came from. That should help in the auto migration. If you want to check that everything worked right, make sure you have a SmartStart CD handy to boot to. That has the Array Configuration Utility on it, and will be a better test to see if things are back, before letting an OS poke at the disks. For servers of that era, SmartStart 5.5 is the last version they will boot, and it is free to download.