I’m thinking for the LS engine family:
Bank 1 Sensor 1 is the front O2 before catalytic converter.
Bank 2 Sensor 1 is the front O2 before catalytic converter.

For LS engine swaps without catalytic converters I delete:
Bank 1 Sensor 2 rear O2 after catalytic converter.
Bank 2 Sensor 2 rear O2 after catalytic converter.