Kutter probably has a better way, here is my way.
Make sure the new hammers fit. Heat the new hammers to a bright red, quench in oil.
May be 4140 castings. Check hardness with a file. If hard, polish bright and reheat to a blue.
If soft after quench, caseharden the hammer nose with Kasenit, Cherry Red, Hard-n-Tuff (what ever you can get) according to the instructions.
Should hold up better. Different process for hammers with sear notches.
Chuck