Mike, Hi. This is Kayo, again. Modifications? None. Twenty-five minute job. No modification to the original wire harness is necessary at all. All you have to do is unplug the two wires that are on the Bosch coil, next remove the two hold down nuts on bracket which is holding the coil to the firewall. Visually look at the Bosch coil. Look at the "shape" of the fittings and the markings on the coil which is marked negative (-) and positive (+) terminal, before removing the fittings. The fittings are different. The shape of these original fittings on the coils are made with a male and female fit and the wires in the car's harness plugs are respectively and complementary to these fittings. You really can't make a mistake on re fitting the wires plugs. Remove and reused the original fittings from the original Bosch coil. These fittings are held down with hex nuts. The fittings are made of brass. Clean them if they are tarnish or slightly corroded. Replace them, if they are in poor shape. Transfer them to the MSD coil with the positive fitting to the positive side and negative fitting to the negative side. Both the Bosch and the MSD coils are marked ( - ) and ( + ). Use the new hex nut supplied with the MSD coil to secure these fittings. Do not over tighten or you may pull or brake the terminal and its housing. Reused the old bracket from the Bosch coil or you can get a new bracket and install it on the MSD coil. Do not over tighten the screw that clamps the coil on the bracket. You can deform the coil housing and create a leakage. Most ignition coils are generally fill with oil and the MSD and the Bosch uses oil. (The oil is for cooling and insulation. Leaking coil will result in a poor and or erratic ignition performance.) Then mount the MSD coil back on the firewall and refitting the wire harness plugs onto the MSD coil (use dielectric grease on the terminal). Double check everything, then start the car up and enjoy the difference. The cheapest way for more performance and driving thrills, and if you don't like its performance -- reinstall the Bosch coil. Nothing to lose except $50 and 1/2 hour of time. Kayo #5508 Lic. 9D NY