Check your reloading manuals. About any starting load for a 158 grain lead bullet, whether RN or SWC, can be substituted. Generally, swaged bullets are not driven as fast as cast bullets. Watch out for those Cowboy Action loads as they tend to be on the light side.
Generally, the same velocity from a 357 Mag case will require a bit more powder than from 38 Special case due to the greater volume.
No problems with the carbon rings here either. I just clean the cylinders a bit more frequently when shooting 38 Special cases in my 357 Magnum.