I had to return 81812AGO3B to the dealer for an exchange. Superficially it looks identical to the "3A" harness that is original in my car, but the wire colors do not all match. I called the dealer parts dept and they told me they made a mistake; based on the VIN I supplied I should have been shipped 81812AGO3A. My car was built in Nov 2004.
SubaruPartWholesale paid for the return shipping, and for 2-day shipping on the correct 3A harness, and I paid $29 for the 3A harness. The 3A harness costs $29 more than the 3B harness.