New harnesses, if still available are very , very expensive. Last I looked the headlight to dash harness which includes engine wiring was over a grand. With a grand and lots of time,you could fabricate your own but finding color tagged wire in every combination that mopar uses in the harness would be impossible most likely. If you developed some other method of coding wires, you pull a harness, spread it out on big sheets of plywood with all coverings off bundles and duplicate lengths, ends, ect. Other than ohm checking each wire out for continuity and checking for contact between them I know no other way than visually checking them too.
Which is the reason for.....run engine play with wires. Multiple problems often need the play with wires aspect to narrow a problem to a specific bundle,area,or connector. It is just a step.