The trite answer:
Call Stein, get quote, write check, receive harness. sorry, too easy a target
But seriously,
I assume you have the installation manuals for each piece of equipment.
What you may need is a hint on how to organize your thoughts to fit YOUR PLANE.
Start with a clean sheet of paper and draw a box on the left of the page to represent the avionics piece you are wanting to wire. Only one box on the left side. Avionics that it will be wired to go in the right side. Multiple boxes on the right. Draw the wires connecting them. And at the ends, write down the appropriate D-sub connector pin number.
For the 4 electronics you list there will be one drawing each. You want a drawing that has the "piece of interest" on the left. One for each. Yes there is duplicate work but it is worth it.
The most complicated drawing you will do is the one with the D180 on the left. You don't have to start with that. You can do the GTX327 on the left (only about 6 wires total on that, including power and ground). Do the simple ones first. Each of them should be pretty simple when looking from the perpheral piece towards the D180. Then move to the more complicated D180 one (maybe with a bigger piece of paper) and use the completed drawings (in reverse) to create the D180 schematic.
If you can find some help in your locality to accomplish these schematics, you can thank that person and then go execute the wiring job.
Good Luck.