You may want to try pressing the Caps Lock button again...we'll all thank you for it.
Your 96 LS does have two O2 sensors. one in the header and one in the cat. O2 sensor placement is as follows.
OBD-I
LS: Primary O2 in the header collector, nothing in the cat.
GS-R: Primary O2 in frontside of cat. No O2 bung in header.
OBD-II
LS: Primary O2 in the header collector, secondary O2 in backside of cat.
GS-R (94-99) Primary O2 in frontside of cat, secondary O2 backside of cat.
GS-R (00-01): Primary O2 in header collector, secondary O2 in backside of cat.
Type R: Primary O2 in header collector, secondary O2 in backside of cat.