My best guesstimate is around 200:

7x767 @ 6 crewmembers per plane* = 42
2 747s = 14
31 mandatory retirements
—————-
87 bare min

add:
30 extra retirements
50-75 catchup hiring
——————

*someone posted average #crewmembers/plane, I don’t remember what the actual numbers are.