You need to decide what velocity levels you want for each caliber. One powder for .38 plinking loads and full power .357 loads isn’t going to work. And realize that plated 158 gr bullets are a poor choice for light .38 loads because of the risk of sticking a bullet in the barrel. And without a crimping groove or shoulder they are also a poor choice for full .357 loads. So more details about what you want to do with your loads would help.