tail lights, trailer brake and fuel gauge, not fuel pump on the '03
i discovered after dropping the 7.3 in the truck that the 6.0 cab's firewall is set back about 1.5" vs the 2003 truck so there is lots of room to remove valve covers now.
i ended up splicing the 2006 cab wiring to the 2003 cab wiring which has been interesting and very time consuming. Ford did some crazy wiring in the 2003 that makes no sense. in 2003 the front seat belts have a solenoid connected to the air bag computer under the dash. in 2006 they didn't do this but the 2006 air bag computer communicates with the 6.0 pcm
so I think I'm going to end up changing out the front seat belts.
the speaker wiring in the '03 was designed by someone that should be in an institution with the wiring running in circles around the cab. i am going to abandon that and run new speaker wires.
the fuel gauge wiring has a wire that goes directly to the wiring harness through the floor on the left side of the driver's seat, the other fuel gauge wire goes from the cluster, to the passenger side kick panel, under the front seats and out through the driver's side wire harness..... along with the trailer brake wiring too. i am still shaking my head at this.
the 6.0 fuel pump was easy to wire up (didn't wire the heater) the 6.0 fuel lines were too short but are easy to junction with the flexible lines from the 2003
the 2006 uses 3/4" heater hoses, '03 uses 5/8" so i had to adapt that
i still need install the transmission/t-case but that's all straight forward. i'm going to adapt the '06 lines and filter to work with the 4r100
somehow. i am going to use the 6.0 trans cooler, intercooler and a/c condenser.
all in all, it's working out well. i couldn't see a body swap being any easier. the underhood portion of all of this is the easy part. dash and wiring is the part that sucks but using the 6.0 wiring is keeping me from having to completely disassemble the interior of the truck (I hate interior work)