both after cat O2 sensors have 4 wire(black/white/white/gray) unlike the before cat w/c has 3 wires(black/white/white). The (4) replacement sensors I bought are all 3-wire Bosch #13913.

Should I:
1) Return the other 2 and get a Bosch 4-wire equivalent? What's the Part# equivalent?

or

2) Rewire the existing harness(4-wire) to the replacement 3-wire sensor...how? Per Bosch specs the Gray wire is ground.<ul><li><a href="http://www.boschusa.com/images/OxygenSensorInstall.pdf">Bosch Oxygen Sensor Installation Procedures</a></li></ul>

Problem is, your parts source still has, and is selling old stock. Until his old stock is depleted, they probably wont have the newer style O2's.