For a Chief's Special of that vintage any standard velocity 158 grain RN, FN, SWC or 148 grain WD would be ideal for target shooting and practice. For self defense I'd go with the old "FBI" load which is normally a Remington 158 grain SWCHP +P. If shot in small amounts there will be no harm to your vintage revolver. Another viable SD load would be the Speer GDHP 135 grain +P but that might shoot a little low at farther distances because of the lighter weight. My favorite 38 special SD load is normally the Buffalo Bore "Heavy" 158 grain +P SWCHP-GC but for a revolver as old as yours I would suggest avoiding that one as it is a bit too much.