Dash Wiring harness, and T-5 swap

[jmel]

Ford fixed the fog light wiring problem in mid-'89, so I doubt that is the cause of your fire. The '84 wiring will not work without modification, because the '87-up cars have different turn signal/wiper/brights switch on the steering column than does the '86-down. If your connectors are still okay, simply re-run new wires going to them by following the electrical diagrams for your car. As for the T-5 swap, you will be taking a giant step down in performance buy using a T-5 from a '84. They are nowhere near the performance level of a 89-up, and even the newer T-5s are barely up to the task of holding a 5-liter's torque. However, if he is willing to sell you all the necessary parts needed for your swap, then it is a good price for the parts alone. It sounds to me that the T-5 he is offering is either blown up or out of a 4-banger. Buy the swap parts, and invest in a World Class T-5.
P.S. I am parting out my '89. If you need wiring, let me know.. Jake