I think Salmoneye gave sound advice there. Slug the bore and chamber throats so you know what you are dealing with and buy the bullet to fit best. On that's about half a thousandth under the chamber throat diameter is ideal, as long as tha's over the groove diameter of the rifling, but not by more than a couple of thousandths. I would avoid going more than two thousandths over groove just because I've seen that deteriorate accuracy. If that bullet turns out to be over .357", then the .38 Special die set will overwork the brass during resizing by making it narrower than necessary and you'll have to expand the overly narrowed brass more at the mouth to get the wider bullet started in. Both will tend to shorten brass life. If you have to use a .38 Special sizing die, I would at least get a Lyman M die
in .38 S&W to do the case mouth expanding.