Vern,
I cant tell for sure by my catalog,but they show 821-16 and then a performance series,2921-16. States that it is designed for elevated spring pressure . One piece pushrod seat. Im pretty sure thats still a separate piece from the main body though.
Then a 2901 with an EDM hole. Then a 801-16 is a .904 that oils the pushrod. Guess they just changed the 821 at some point in time,I thought maybe I had used different numbered ones.
They also now offer three different tool steel .904 lifters.
Keith