I also have an old home with many "details" that do not meet current code, including my basement stairs. I have some plans for the house which include changes to the stairs, but I have not gotten to that project yet...
A lot depends on your local municipality. What i have been told by our inspector is that with an old house where existing does not meet code, you can replace like with like. For example, I need to replace my porch railings (porch is about 32" above grade.) and the original railings were only about 24" high. Because of the existing column detailing, installing 36" high railings would make it look terrible. He tells me that as long as I am going to replace existing, in place railings, I can stay with the original height.
A lot depends on your local municipality. What i have been told by our inspector is that with an old house where existing does not meet code, you can replace like with like. For example, I need to replace my porch railings (porch is about 32" above grade.) and the original railings were only about 24" high. Because of the existing column detailing, installing 36" high railings would make it look terrible. He tells me that as long as I am going to replace existing, in place railings, I can stay with the original height.