drain out the pentosin from your mustang, save it for the 86, ok to reuse, if its not dirty
refill with one of these
http://www.oreillyauto.com/site/c/de...2281&ppt=C0207
[ame="http://www.amazon.com/Torco-A220085C-Automatic-Transmission-Bottle/dp/B005DTWTJS"]Torco A220085C HiVis ATF Automatic Transmission Fluid Bottle - 1 Liter, (Case of 12) : Amazon.com : Automotive[/ame]
lmk, think you will like the torco in your Mustang! I'm a bit of a fluid geek, so if you try it PLEASE let me know