One thing I've built for a few swaps etc...is a patch cable. Meaning if you take the interior harness piece for the engine harness you are using and the engine harness piece for the interior harness you are using and you map them out, then solder and heat shrink the wires, you make your self a piece that connects and keeps you from hacking the engine harness or interior harness. It also allows you to easily fix any wiring issues you might make.