HI, I have a friend with the same truck and his did not come from the factory with the wiring harness installed!They install The Heaters but sometimes they don't come with the Wiring harness, you have to pay extra he was told,Crazy I know? I have an '04 F350 and mine is located just to the left of the right side Driving light (look to the left as you are standing in front of the truck) Ihope this helps, John
Search Ford F-350 Super Duty Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Ford F-350 Super Duty Experts