I can only answer part of your question, I tried to use the double spring with a modern hammer and it wouldn't work, wouldn't work with an older hammer in a new frame either, but in an old frame the late single leg spring might work, but the anchor point on the hammer if it has one, is different. I tried bending one of the double springs to make it work, but it broke, sent the rest back for credit.
What will work with an old hammer is a 60 cent hairpin spring from the hardware store, it can be bent to what ever shape needed if there's an anchor point on the hammer.
Tim