I'm not sure how the factory setup goes, but why not just get the Hoppy wiring harness w/converter? They're only like 40 bucks at Napa.

http://www.trailerwiring.com/cgi-bin/view.cgi?part=43415

You'll probably be able to pull out the factory one while you're in there, which may not be more than the Hoppy adapter with a Toyota sticker slapped on it.

My Truck: 1987 XtraCab DLX 22R 4WD 5 Speed Manual
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"Speed has never killed anyone. Suddenly becoming stationary, that's what gets you." -Jeremy Clarkson