This solution has proven to be superb! I can now run My Mac Pro in a dual boot mode with either OS 10.7.5 or OS 10.6.8, choosing one or the other through System Pref. Startup Disk. I cannot thank Roy Miller enough for his persistence and expertise as well as generously giving support to all who needed it.
It is a lengthy discussion and several other folks lent effort to the fray that are to be thanked as well.
My specific requirement, getting some older expensive hardware to work in OS 10.7 or later, that is, writing appropriate drivers, was not going to happen according to the manufacturer. So, OS 10.6.8 was the last best chance!
Thanks to you for bringing this to my attention!