Good morning Jim,
Glen was fairly particular about his electric 12's, so I have a good chance of getting this one right. He was extremely faithful to his Ovation Bluebird 12 String
. He played the BLuebird 12 string from about '77 to around '91, when the guitar was damaged by the airlines. When it was damaged, his sideman Jeff Dayton
took it to Ovation but asked that a Hamer 12 String
be crafted to Glen's Bluebird specs and his preferences. He played the Hamer from the 90's until he quit touring. So, from the mid 70's, until he quit touring, Glen was typically using one of two electric 12's.
Looking at YouTube, it appears that Glen is playing the Bluebird 12.
In terms of amps, maybe Paul or Wayne can stop in and share their thoughts on that.