Wiring harness mods

[nwarky]

Before posting this thread I reviewed this forum and failed to find this info. I am beginning the conversion of an '87 Turbo Regal to an LS3/4L65E. I plan to use the stock fuel system as much as possible, the factory A/C system and plan to totally replace the original dash. I should confirm that all factory options were functioning when this project began. Oh, BTW that Powermaster is outta there. Here is where I need help. I have the GM ECU for the LS3 and a separate GM controller for the 4L65E as it is a part of the Connect and Cruise "kit". How much of the factory wiring harness do I need to keep? Obviously I need to keep the front, rear, and interior wiring circuits as well as the ignition system. Other than isolating the wires for the fuel pump and A/C system do I need to keep any other wiring from the original harnesses? The A/C system has me the most confused which doesn't take much to do. I want this to be neat and clean yet remove all unnecessary wires. You know, have it look like a surgeon was there rather than a butcher. Any knowledge will be helpful. Thanks!