Here's find some cool varieties of Mustang wheels for your pony car. I've provided links for you to check them out for yourself.
Since many of the major aftermarket rim manufacturers make wheels for many vintages of pony cars, I've grouped them by manufacturer and provided some pictures to give you an idea of what's available. Click on the blue links for more detailed information or just click on the picture of the wheels you like. Links are at the bottom for some of the major sellers out there as well.
It used to be, that if you bought these kinds of wheels over the net to save money, you still had to find a qualified shop to install them, but these days, a number of these companies have local partners to install and balance them and may even deliver them to that shop.