I have had very good luck Lectric Liminted
www.lectriclimited.com . For the most part (for me) they are a plug and go harness. Most everyone else would use them right out of the box. Some things I do change over to OEM plugs as the aftermarkets are not correct. I have never had any issues with them whatsoever.
On the engine harness, I clean off the black electric grease from the terminals as this has sometimes caused connection issues. Easy to fix while doing a restoration but a real pain after the car is done.