bruce_miranda

this can be done. I have converted atleast 5 sets of M5 mirrors and 2 sets of normal mirrors, both ways i.e. 1 plug to 3 and 3 plugs to 1.
The biggest challenge in doing this is the plugs used on the mirrors are not sold as spares. So to work around this you have got to find a set of mirrors with all the plugs needed.
You say you have the original wiring harness from the old mirrors. So that is a big plus, you will need that.
Next you need the motors from the original mirrors too. If you don't have that then try and use the motors on the M5 mirrors you have by just removing the ECU plugged into the motor inside the mirror. I don't know if the motors themselves changed between Sep05 but I know that there are atleast 2 variants of motors in all cars, one that doesn't have memory and one that has memory.
Start from there and report back. The pre-Sep05 mirrors are actually dead easy i.e. everything is wired externally, there are no 'brains' inside the mirror. The post-Sep05 has the ECU built into the mirror and worse still inside the plug that goes into the motor.