Rearview mirror wiring help

[amwitched]

I have a 1991 Toyota pickup and I am replacing the review mirror. The replacement mirror has 3 wires (2 black and one red). The original mirror has a clip that has only 2 wires (1 solid black and 1 black/white stripe). How would I go about wiring this?

[Harry Chickpea]

Red is positive
Black is negative (ground)
Black w/ stripe would be controlled

My guess is that the new mirror has a side-to-side adjustment as well as an up and down one. You'll want to sort that out if it is the case.
Without seeing a schematic, I would use a multimeter.

Measure DC voltage on the clip and note polarity.
Put one lead to the chassis metal, use the multimeter on DC voltage to note which lead is hot.

Put one meter lead on the chassis attachment of the new mirror, set it to ohms or continuity then test each wire. One or more will short to the chassis. Those are negative. The other(s) by definition are positive and controlled positive.