No check engine light on the '86GT, or my '87Notch for that matter.
Hooking up the "kickdown" cable will be difficult, since that's not what it is. It's actually called the throttle valve (TV) cable, and the AOD uses it to change shift points AND shift characteristics. On a C4, it's a true kickdown rod for downshifting, and that's going to be the tricky part, since you need it to "hit" when the throttle is open far enough, another reason you see C-series trannies on carbed and TBI cars. As far as making all of this work, I haven't a clue. Seems like you should be able to hook up some sort of bracketry and trim the cable some way. Remember you need that kickdown lever on the C4 to be full down at WOT. Good luck.
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Capri306, Moderator, The Mustang Works Online
1979 Mercury Capri, 5.0L -- C4 -- 2.73
1987 Mustang LX Notch 
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[This message has been edited by Capri306 (edited 02-05-2001).]