1999 Ford F-250 and F-350 Super Duty Trailer Wiring Fastest shipping available and a lowest price 1999 Ford F-250 and F-350 Super Duty trailer wiring guarantee. Expert lifetime technical support on all purchases. Complete 1999 Ford F-250 and F-350 Super Duty Trailer Wiring installation instructions and customer reviews. 1999 Ford Trailer Wiring | etrailer 7-Way OEM Replacement Trailer Wiring Harness for a 1999 Ford F-250 Super Duty; You can use the Curt T-Connector Wiring Harness, # C55243, or the Tow Ready Replacement 7-Way Harness, # 118243, on your 1999 Ford F-250 Super Duty. These are basically the same item for your truck made by different manufacturers.