Some well-preserved Mayan Codexes would be a great find.
It would, but probably not gonna happen. Even before the Conquest, the archives of rival cities were destroyed by the victors, who also then savagely tortured the ruler and his family to death over a period of hours or days.
Michael Wood, in his “Conquistadors” documentary (must be available, I got a copy for Xmas) shows an otherwise unknown codex, which survived and has been hidden by the local yokels — the alternative being, it’s post-Conquest in date, and may not be all that useful.