holy shit man .. now that is a MAJOR job and a half since every thing is different .
thing is . you wont find a allready made harnass since it is not a popular swap cause its just to much work.. but you can completely rewire the car if you have the time and most of all the patience.
Now just one question here. when you are saying from a 86 to a 93 you are talking about swaping a 2JZ series engine in you MkIII right ??
If that is the case you are in for a lot of work.
i had a few sites on that before .. ill see if i can find em for ya ..