Hammer blocks are frame specific. However, any N frame hammer block will fit any N frame, whether frame or hammer mounted firing pin. Many times people who do "action jobs" will leave those out because they can get a better action without it. I keep them in all my guns, as I feel it's an important safety mechanism. The key is to work them over just as you do the other parts so it doesn't add any roughness or hesitation to the cycling of the action.

To do this, you have to look at the key points that this part can cause a problem.
They are - 1 at the top of the flag where the part rises up past the notch on the hammer, just under the firing pin,

2 the sharp edges around the bottom where it was blanked out in the punch press die, and

3 the hole that the rebound slide pin rides in.

To address these issues -
1 Radius the top of the flag and the bottom corner of the hammer and the corner of the frame where the flag may momentarily catch as it returns upward. The new F/P in frame frames are already radiused there.

2 Round or chamfer the sharp edges of the perimeter of the bottom to eliminate any drag points.

3 The inside of the hole is rough because the punch press operation leaves a ragged surface, the same as around the outside. Use a needle file to smooth up the inside of the hole so it will be smoothly and evenly activated up and down by the rebound slide pin.