I'm pretty sure the stock wires are 8mm.
I'm using 9mm wires, so I had to "modify" the stock looms and get some ford motorsport looms to "pretty" it up along the sides.
I think you'll be fine with the stock looms with 8.5mm. If not, you can always go the same route I did...
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"The Yellowjacket"
Ricer 1: What the heck was that!?
Ricer 2: I don't know. It looked kind of like a yellow SN95 Mustang.
Ricer 1: Nah, fast SN95 Mustangs don't exist... Must have been a mirage or something...