Done the board swap. Lucky I had a donor board with same firmware version and only a few serial numbers apart as donor for the cloning, then I put the board back, as the person whose computer it was had nothing to do but catch up on her filing. Drive was for something that was no longer supported officially by the supplier, and they had no longer any media to reinstall. Made 2 copies though, then swapped the boards and put the donor back in the machine. It worked on both sides, and I grabbed another drive to make the second copy, and wrapped it up in some antistatic bag and bubble wrap, and popped it into the case as a spare.
Murphy dictated I never needed that second spare, though I did then make monthly full backups of the drive, though as it was running Win98 that was fine, only a 40G drive, the giant zip file was easy to store and compressed well, seeing as the data was almost all text files with predictable structure. I still have Win98 media to reinstall, complete with the COA and the DVD, all still shrinkwrapped, 2 copies........ Then another 2 DVD's with every single patch Microsoft ever offered for Win98, including all service patches up till EOL.