The MSD-6T comes with a shock resistant mounting kit that makes mounting the box on the firewall next to the battery very easy. The MSD box, like most aftermarket ignitions, replaces the stock system. It takes its trigger from whatever pickup is in the distributor and fires a coil. It wires somewhat different than stock because it has a high peak current draw. A power supply lead wires directly to the battery.
New wiring is installed to the distributor and coil.
One modification that must be made with the MSD system is the tachometer hook up. This signal, however, is too low in amplitude to trigger the Z tacho. Then disassemble the tacho and find the large power resistor that is in series with the tacho input. There are typically two resistors in series with this lead. One is physically large and the other is not.