I don't know what else is available, but the Helm's diagrams provided everything I needed to do the wiring diet on my donor harnesses and the diagrams only cost $12.
The Helm Electrical & Vacuum Troubleshooting Manual (EVTM) has the diagrams for every circuit and is much easier to use than the normal diagrams. (I have both) The EVTM also has a short descripion of how each circuit works. Used it to strip my harness. No problems. Part number is FPS-12121-XX. Insert the last two numbers of the model year in place of the Xs.
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