IIRC, the 03-07 tow mirrors have a long harness with different terminals than the 01-02 tow mirrors. The 03-07 harness is physically longer than the 01-02 mirrors because it goes all the way down to the door switches. You may have to do some splicing to the harnesses but they will physically bolt up just fine. I'm pretty sure the heat function works in conjunction with your heated back glass window.
Here are a couple diagrams showing pinouts for the 99-02 stock mirror.


See here for info on the turn signal integration.
Where abouts in Maine? I'm in Old Town.
Last edited by bartjo06; 06-07-2012 at 08:38 AM.
2001 GMC Sierra SL ECSB - Project
2012 Honda Civic Si - DD
2009 GMC Sierra SLT ECSB - Sold