i believe you would find American Autowires instructions to be exactly what your looking for and they have a good tech support if you would need it.

From what I seen painless is for basic wiring needs. You may be able to fine one that would work but from what your description says some mods will be needed. I would look around and see what's available. Make a wiring diagram added to whatever you get for future reference. Another option would be to check out some early 80's cars wiring harnesses that maybe could be used. There you will already have many different wire colors and a factor wiring diagram. From that modify it to work with what you have. Years ago you could walk around junk yards and look for something like this, Today is another story.