I have Section II Part D from 1998. This is before the Code changed from the old safety factor of 4 to the 3.5 used in the current Code. The Code was very slow moving before that and thus I would expect 1973 to have the same allowables, but perhaps someone else will have pages that old.
For SA516-60 the allowable is 15.0 ksi (60 ksi tensile divided by 4) up to 650°F. The allowable tapers off above that.