Which coil?

Dana67Dart said
For the record...

If you originally had a 5 pin ECU you need the 4 post ballast.

If you originally had the 4 pin ECU you don't need a 4 pin ballast, as the ECU is internally regulated.

The 5th pin was the power to run some of the electronics.

The 4 pin did away with that.

Also if you changed out your 5 pin for a 4 pin ECU you don't need the 4 post ballast.
Click to expand...
If it was mine, and it originally had the 5 pin ballast, I'd get the 4 pin harness just to do away with that and convert to the 4 pin harness and two pin ballast. Those harnesses were sometimes a point of contention. I have a friend who found out the hard way.