A 38-44 bbl can be a project for a liner especially if you are going back to the original 38spcl caliber.

It keeps the original bbl on the gun with it's ser# and all, but can give you a new bore of course. Also there are many more smiths that can do relining than do rebore/rerifle out there.
You'll need the bbl recrowned and a new forcing cone cut of course.

A liner for the project can be turned from an otherwise bore perfect M&P 38sp bbl of length that leaves you with enough to do the job. Keeps S&W specs for you in the bore that way if it matters.

Otherwise nice 38sp spec liners (and most any other caliber) sold by the inch (hammer forged) are sold by TJ's Gateway Enterprises, Alexandria, KY 859-635-5560 is the # I have for them.
Track of the Wolf muzzle loader parts sells some of his liners/calibers but not all of them. Don't know if 38/357 is in there., They also charge a little more than buying direct, but you can see what's available.

If the outside of the orig bbl doesn't have a cosmetic defect in it from a bulge, then that can be left alone and usually no refinish is needed. If it has the snake ate the rat look,,then some draw filing and polish work and reblue will be in order. A new bbl would probably be a reblue job too especially if it's a reworked 23.

Just another way to do it.