Any reason why to swap it out? You can go with .38 +P and be close to magnum power. That said, the swap shouldn't be a big deal. As said, make sure the b/c gap is ok and it times correctly (it should, Ruger parts (within a model) are pretty interchangeable with little to no gunsmithing needed).
However, seeing how litigious things are in the US nowadays, if it were used (with the mag cylinder in place) to defend yourself, and it is examined by the shootees lawyer or a zealous DA, they are going to hammer you with questions like "why did you make this .38 into a .357 Mag? Were you looking for trouble? Etc., etc., etc. Even if you win, then the shootees family takes you to court for unlawful death where the proof does not have to be as much as a criminal case for them to win a bunch of money from you.