THere's a whole series of Saturn Quarterly report movies from the 1960's. MSFC has them on Youtube.
Here is one.
One of the mind-boggling things they did, is when they needed to stack a whole Saturn-V to see how the 3rd stage and spacecraft fit with the tower interfaces. But they did NOT have a 2nd stage available (I know a 2nd stage blew in testing but do not know if this is why one was not available then or a schedule issue). Anyway, they made a 2nd stage simulator, like an end-on dumb-bell. Say an 8 foot diameter steel pipe about the length of the 2nd stage, with circular bulkheads at the ends (reinforced with struts/gussets), to interface with the 1st and 2nd stages.
It may have been made as a "Pathfinder" to work out handing, transport, and crane operation work before then.
I saw it in a couple of these Saturn reports, but do not recall if it was in this one and I do not have time to look.
Also, in at least one, perhaps more, of these quarterly reports, the narrator seemed to be the same voice as the famous "the missile knows where it is, by knowing where it isn't" video's narrator.
