Custom Wiring & T-Connectors - curtmfg CURT custom wiring allows you to outfit your vehicle with a standard connector for plugging in trailer wiring. Each T-connector is vehicle-specific and plugs into existing wiring without any splicing required. Our custom wiring is also thoroughly tested for reliability. Learn More Amazon: curt t connector wiring harness: Automotive Amazon's Choice for curt t connector wiring harness. CURT 56040 Vehicle-Side Custom 4-Pin Trailer Wiring Harness for Select Subaru Forester, Outback, Sport, XV Crosstrek. 4.8 out of 5 stars 485. Automotive $28 $ 28. 95 $30 $30. Get it as soon as Wed, Aug 21.