Those shims will work but they also have resulted in broken shafts. Weight your options before making a choice. Sometimes a new set of pushrods is cheaper than repairing the damage.

1970 Duster
Edelbrock headed 408
5.984@112.52
422 Indy headed small block
5.982@112.56 mph
9.42@138.27

Livin and lovin life one day at a time