WOW

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[email protected] 2x" width="20" height="20" /> :-& . You probably would be better off replacing the entire wire harness from the sound of it. That can be done, but takes a little time. One way to get one is to find a junker and remove the harness from it, preferable one from an 86. Though an 85 would probably be close enough.
If you wanted to try rewiring, you will need a real good diagram, not the one in Chiltons, but from a EVTM for 1986. You need to know where each wire goes and the proper size. That would be pretty difficult to explain in a forum post.
Find an EVTM in any event, they are listed on e-bay from time to time. If you find someone on e-bay dealing in automotive manuals and they don'thave one listed, email them and ask. They may not have it listed yet or can perhaps notify you if they find one.

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[email protected] 2x" width="20" height="20" />
The short of it is that you have a real challange if you plan on completely rewiring it yourself. A new harness will save you a lot of time and headache. You will have to take the dash apart to remove and install a new one. It is possible you might be able to get a after market harness, but they don't cover everything in your truck.
Good luck,

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