I've read the FAQ, and see there is no equivalent IPv6 for our lovely 44/8. My question is, can we utilize IPv6 with our IPv4 address embedded in it? The reason I want to be able to easily utilize message authentication with IPSEC AH.
As the discussion got sidetracked into unrelated issues, let's go back to the question. What exactly are you trying to accomplish? Of course it is possible to make some form of tunnel over IPv6 between two AMPRnet systems, and transport the 44/8 IPv4 traffic over that. But you will have to admin both sides of the tunnel. The existing tunnel network operates only over IPv4. When you want to make your own branch, that connects to an existing place with AMPRnet connectivity, and you want to do that over IPv6, that is certainly possible.
Rob