What a nice project!!
You may find all the tire decals you may look for here..
http://www.fireballmodels.info/wl.htm
I used them om my latest project, they work great!!
I have all issues of these 1962 from AMT, and the last reissue of the Bel-Air (red on box) and the Impala convertible has the right and accurate grille included...
What means that a model is just perfect, is when you can't tell wich one is the real thing!!
Your Mustang is just awesome, the cleanest build of that Mustang i've ever seen....