When I was trying to decide I tried to find as many pictures with the kind of wheels I was looking for. This is really a personal choice. One of the factors in my choosing the 14" 500s was that I had just purchased tires of that size and couldn't afford to buy new tires and wheels (BW, the wheels were a birthday present-any chance yours is close??). Try www.google.com as a search engine. That's where I found all my pix.
I forgot about a website that you can choose from a bunch of wheels on many years Mustangs. Unfortunately, I didn't bookmark it but if you do a search here on "wheels" I remember someone giving it out. Sorry I can't be of better help.
the website that a couple of people talked about it cool. I sent the guy a picture of my car, and he put it in the website. Now, I can bring my car up, and change the wheels, and raise and lower the car, at any time...
Go to the site, and click on the "white" (car is realy yellow)'70 Mustang, and pic of mine comes up...It is great.