I've used YnZ to reproduce my 1960 harnesses with nothing but outstanding results. Reproduction of the harness will take a few weeks, as YnZ assembles the harness then sends it to another local shop to mold on the correct plug ends. In return, you will receive a harness of exact appearance to that of your original. For your situation, simply you can work with YnZ to add or delete any wires to your reproduction harness for your add-on accessories. Unfortunately, any changes you make to the harnesses feeding into the firewall may warrant alteration of your dash harness.