Your 2008 Harley Davidson Heritage Softail Classic Anniversary uses a 5 flat because motorcycles have turn signals on different circuits/bulbs than the brake lights. Since your trailer has combined turn signals and brake lights on the same circuit, I recommend The Upgraded Circuit Protected Tail Light Converter with 4-Pole Flat Trailer Connector # 119178, which will combine the separate circuits on the bike to the output side of the connector.. This wiring harness adapts to your Harley... view full answer...