Dunno - according to the Tommie Vaughn Performance website ( http://www.tommievaughnperformance.com/M-4204-F318C.aspx ), the proper number from FRPP is M-4204-A28 for the Auburn, and it should be M-4204-F288 for the Ford part.
MM&FF has the 28-spline for $200 from Tommie Vaughn.