help on my tattoo for my car

I don't know about a symbol, other than to use the traditional running horse, something along the lines of what StDr proposed. It's a universal icon, so it's kind of hard to deviate from it. Unless you just do something like a horse, or horseshoe. But, then, you have to explain its relevance if someone doesn't know that you have a Mustang.

If you put the name in your tattoo, then you have an almost perfect name if you want to try this idea: Use the famous 'mach 1' font to write the name Nancy in the tattoo. If you have a good artist, they can use the 'M' as a template for the 'N's, and you have the 'a' and 'c' already. All they need to do is freehand a reasonable 'y' to match the other letters.

I hope my explanation of the name/font thing makes sense. It's getting late and it's been a long day. If it makes no sense, just tell me. I'll try again.