I have a 1979 Super Record rear derailleur that came with aluminum pivot bolts (shipped directly from our friend Matteo of Firenze Italy). Somehow I lost the upper/mounting bolt. The aluminum bolt was just a bit smaller in outer diameter than the normal titanium bolts, at least for that year. I was unable to find an aluminum bolt at all, or any TIs that would fit in, so I finally used emory cloth to reduce the diameter of a TI bolt, and it worked fine. Hope that is some help.
Best regards,
Mark Agree
Detroit MI