Can i just changed the head unit in a 99 460 mach equipped mustang.   Is it like any other car and just have to buy antena harness and face plate.  Is the a harness a special one since they have cd and stero seprate. The harness it strait forward with matching colors or do i need a wiring diagram.  Please excuse the grammer. Help would be appriciated.  Trying to help a freind out
      can anbody help me. Im just a girl trying to save instalation charges
 
      Changing only the headunit will require installing Output Level Converters (Scosche makes them).  There are 3 factory amps with the Mach 460 system that have specific input requirements that the Output Level Converters allow you to adjust.  https://www.crutchfield.com/cgi-bin/S-nAF9dtIh9iK/ProdView.asp?s=0&c=11&g=751&I=142CFDK6++
Check out this page for info on the system (locations, specs, etc...).  They're from a '95, so it wont be exact, but it will get you started  https://www.flemworld.com/95/mach.html 
Check out this page for info on the OEM wiring harnesses https://carstereohelp.com/wireharnessFord1.htm
You can get the new installation harnesseses at your local car audio shop.  Using them will make life easier for you, and allow for a cleaner install.  
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      thanks for the help. The kit i bought came with three different harrnesses. I only used the power harrnes and a harneess for the speakers  to worj with the amo. The faceplate they sold was a wrong one so i didnt use it and the stereo fit pretty good with out it.
      I would like to know if I can install 6 1/2" mids in the rear 5 1/4" factory speaker loacations in a 95 Mustang w/460 Mach sys.? Also, I plan to install my stereo sys from my old car into this car and I am wondering how easy is it to replace the factory amps in the factory locations with some higher power amps,and if I go with these differant amps do I still need additional electrical equipment to hook-up an aftermarket head unit?.
Steve, this site is great and has helped me fix several friends car stereos, thanks!