The base on the Taco mirrors is larger than the mirror base on the 4Runner. It is my considered opinion that this mod therefore isn't workable on the 4Runner.
The base on the Taco mirrors is larger than the mirror base of the Dodge mirrors also.
Measured my Dodge mirrors tonight the bottom measurement at the door is 6" on the Dodge mirror. The verticle measurment or the straight side of the triangle is 7 3/4". The angled measurment is 9 1/2".
Hope this helps you out.