Thanks for the ideas.
I've forgotten the details, but I did something that made it more tractable, in that I can run run Linux in a different drive/partition and access /dev/md0 (which requires)--
mdadm --create --level-raid1 --raid-drives=2 --spare-drives=0 /dev/sdb3 /dev/sdc3
which then sees that these partitions already part of a raid1 array and asks for y/n to proceed. Proceeding it then (re)creates the raid1 and /dev/md0 is then available (and it can then be copied, or tar'ed, to an external drive for backup).
When I reboot, and select the "main" Linux that was installed with /dev/md0 it now locates the md0 without intervention (and I forgot what had to do to make this happen...seems like I something was missing that I had to add...).
Even more recent--I've found that save/restore of the whole system works if tar, with an exclude file that eliminates things such as /dev and /proc, is used.
what does mdadm.conf say about the file system (has it changed UUID?)
As far as the raid1 "knowing" the Linux system--I haven't looked at the UUID in the mdadm.conf file. When I get a chance I'll take a look at that.