I would not use a 88 turbocoupe wiring. It has almost all the front end of car wiring in it you would have to remove. I would use a 87-90 Mustang 2.3 non turbo wiring harness and repin it for the vam. Then all would be need to wiring power etc to the connection.
Is your 84 a turbo car already?
I have not seen a 84 harness so can't say. I would say could. I took a 93 Mustang and redone that harness to run a 94 Taurus SHO motor. So I can't see why you can't.
This is the 88 wiring diagram. http://www.rothfam.com/svo/reference/88Thunderbird.pdf
Some info here may help. Maurice
1989 Mustang 2.3 turbo, rebuilt SVO motor, 88 computer,vam upgrade, adjustable boost control, intercooler, c-4 trans
, 7.5 345 turbocoupe rearend, motorsport driveshaft, Black interior.