You're quite welcome.
I looked the schematics once again and the original wire I mentioned is not going to work for you. If you look at schematic of the "MAIN LIGHT SWITCH" on page 2 of; Ford Service Manuals - Wiring Diagrams
you'll notice that the switch actually grounds the signal for "PARK". You need +12V for the dimming input. You need a non-dimmable +12V supply when the parking lights are on. I think you need to run a wire over to the Smart Junction Box (SJB) which is located in the front passenger's kick panel. I can't think of a closer place than that, other than going throught the firewall or into the trunk to connect to one of the parking lamps.
You've got a number of choices here at the SJB. All of them come off of connector C2280D on the SJB. That conenctor is on the rear side of the SJB, so you will have to remove the single bottom nut holding the SJB in to access it. See page 5 of the following PDF which shows you which connector is C2280D on the SJB: Ford Service Manuals - Wiring Diagrams
See the following pages in the this PDF for your choices of wires on that connector: http://iihs.net/fsm/?dir=40&viewfile=Parking,%20Rear%20and%20License%2 0Lamps.pdf
TAIL LAMP LEFT, Tan with Red Stripe, Wire 1784
SIDE LAMP RIGHT, Brown, Wire 14
SIDE LAMP LEFT, White with Red Stripe, Wire 667
SIDE LAMP RIGHT / LEFT REAR, Red with Pink Stripe, Wire 1361
LICENSE PATE LAMP, Dark Green withe Light Green Stripe, Wire 1370
TAIL LAMP RIGHT, Dark Blue with Tellow Stripe, Wire 1729