looking to replace the complete dash assembly as it is in bad shape any suggestions on where I might find one or a custom one at that

 

look around http://www.mustangdepot.com/ http://www.mustangsplus.com/ http://www.mustang-unl.com/ theres a few other only way to get custom one is to pay someone to make you one

 

Are you referring to the whole dash that runs driver's side to passenger side, or just gauge cluster? Either way eBay may be your best bet. Our big body mustangs are still not as highly supported by the aftermarket companies as the 64-70 stangs, but they are getting there.