I purchased the Isolation harness from electricalconnections.com
I dont know if it is the best or worst, but EC had them available
when I needed it. I had to purchase the Trailer Relay Harness p/n 07660, Trailer Relay Sub Harness p/n 07662
and Trailer Relay Converter for the 5 to 4 wire plug p/n 07664 Total cost about $95.80.
Once again the 3 sets of instructions came without pictures, so being the novice I am I will just have to wing it since
I have never seen the finished product before.