As far as we can tell she is pretty much original except for a few things here and there - such as a new dump valve in 1992. We have hooked up with another couple who just purchased a 1969 GlobeTrotter from the original owner. They have exactly the same set up in the back as we do - so I don't think it is custom.
The 69 year was a funny one - they built it in 68 but I think they took the end stock of 68's parts and matched them with parts from the new 70's coming in.
Nevertheless she is a great little trailer - but boy are those $$$$'s adding up. But then nothing in comparison to a new one - or as I have said before those poor people doing a complete rip out.
Will check out your suggestion - but another....for now....we will tote along an extra battery and our battery charger -it will get us by.