Mels 5.0

I'm trying to figure out if a heater control will fit a friend's Mustang. He had the middle arm break on his unit and he can no longer get air or heat in his Mustang. He has been searching for one for months in junk yards, used parts dealers, etc. He was originally told by a junk yard owner that only the '85 and '86 controls were compatible. However, I ran across 3 on ebay. The descriptions say 79-86 heater control but came off of vehicles other than 85-86. None of them can say for sure that it will fit an '86 even though they look the exact same except for the color of the ***** which are chrome (79-84). I have an '85 GT and the ***** are black which are the same in my friend's '86. Can someone tell me for sure if 79-86 heater controls are compatible or does it have to be an '85-'86 specific to fit? Thank you in advance!!