So if the 120,000 # piece is .667 square inches
and the 80,000# piece is 1.0 square inch,,,are the elongations the same???

It depends on their length.

The elongation is: e=PL/EA where e=elongation, P=load, L=length of
piece, A=cross sectional area of piece, and E=elastic constant.

All steels have approximately (withing a few percent) the same elastic
constant, so the tensil strength of a steel plays no part in it's
stiffness, only it's strength. In your case, if the lengths of both
pieces are the same, then the smaller cross section will deflect the
most. All this is dependent on the geometry of loading being able to
accomodate different deflections.

tom pettit