I just replaced the harness in my 71 TR6, I went with the original harness from TRF, and got Dan Masters book too. the wiring has the correct colors so it was easy to install, I did add relays to the head lights and electric fuel pump. I cant talk about the other harness with the relays built in but from the pics I could see when they posted here, I believe the wires are not color coded so its a lot more work and you will have to put the connectors on each wire too. I would go original if you want an easier installation. the only other thing was I bought all new bullet sleeve connectors from british wire and about 20 bullets just in case, and I bought the heavey gauge brown, brown white wire and ran a parallel to the amp gauge and to the starter for my larger alternator.
Hondo