A very hard job to do. Mustang wiring harnesses are complicated things; unless you really know something about automotive wiring and electrical stuff, you're way better off taking it to someone who does.
veryuseful.com/mustang/tech
You will find a free wiring diagram at: www.veryuseful.com/mustang/tech/engine#Diagrams Good Luck!
http://www.moby302.co.za/wiring/diagrams.html
Classicarwiring.com (eBay)
Try MOTORLIT.COM.
You can find a fuse box wiring diagram for a 1985 Mustang GT 5.0 in the vehicle's owner manual. You can also find them at designated auto part stores.
Go to www.the12volt.com they have free wiring diagrams.
When working on anything electrical in a car, it is imperative to have a diagram. A diagram of the cooling fan wiring to a 1996 Mustang can be found in its maintenance manual.
Haynes auto books
the motor will fit but you will have to use the 5.0 mustang motor mounts.the wiring will not work.you will be better off to find a 94-95 mustang gt harness and computer unless you are going carb.
Anyplace there is a need to protect the electrical wiring from an overload or short in the wiring.
go to your local auto parts store and buy a haynes manual. In the back they have full wiring diagram.