More questions than answers. You say you “Saw” a model 13 with a 38 Spl barrel… A 13-?. Was the frame actually stamped as a Model 13 or did a clerk say it was? Next, the “window” for the cylinder and the cylinder (357=1.67” - a 38 would be 1.56”) are longer for a 357 than it is for a 38. You said the 357 WILL camber so it is presumably a 357 cylinder. If it were a 38 cylinder reamed out for 357, many standard 357 rounds would stick out the front of the cylinder preventing it from closing/indexing. You didn’t say what the barrel length is. The Model 13 was only made with a 3” or 4” barrel. If the barrel is a different length, that would explain it being rebarreled with a 38 Spl barrel. As long as it actually IS a Model 13 frame and cylinder, it should be just fine, but I would be inclined to have a gunsmith check it out to be sure.