To the best of my knowledge, the new ones are drilled and tapped for scope only. Nothing for open sights. If I'm wrong, Tim or someone will correct me. I think all you have to do is have the front sight installed. The other holes are there for a Williams peep. I never really got into it too far. My original .357 came with iron sights, but I had to have a scope because of my old eyes.
The one thing I can tell you, the .357s are shooters. I've had two now and both shot one hole at 60 yards.
I've found a third locally yesterday, scoped, that I'm going to ream to Max.
Pete