Tailshaft from ?

DOes no one know where this tailshaft is from ? Its behind a 64 close bolt pattern toploader , but I dont think its origonal.the numbers on the tailshaft are 78ZY-7AO40 . The shifter is blocking rest of it , so Im not sure if there is a -A or -D at end but I assume so . Im just stumped by the first 4 numbers. there is also a big casting od 28-8-80 on side and a oval mark that says Aecho in Mexico under P/N . SO any ideas what Im looking at here?