IF the only difference between the '70 and the '72 harnesses is that the '72 has the extra circuits for the electronic ign & you stated you have added electronic ign then yes I would get a '72 harness. I'm assuming you are using a chrome or orange or some other ECU that is a 4 pinner? If so plug in a 2 terminal "single" ballast that has the ohms you desire to match your coil on the ballast white connector side that has the brown wire on one end, and another 2 terminal "single" ballast side by side of any ohms as it is just there to fill the harness for appearances' sake and it goes nowhere on a 4 pin ECU or a replacement parts house 5 pin which has a dummy 5th pin. Only the factory OE 5 pin ECU's have a functioning 5th pin & REQUIRE a 4 terminal "dual" ballast setup.