well folks from what I have researched,the biggest tire I can go with is a 235/60/15 8"with a 4 1/2 backspace . Gonna go with a 7" wheel up front but not exactly sure what size. Help!!!!

That size rear tire will be a shade over 26" tall. Are you trying to keep all the tire heights equal or smaller in the front, etc,? If you're using a 15x7 rim in the front, a 195/70-15 will be a shade under 26" and a 225/60-15 will be about 25-1/2" tall. If you want to plug & play with different tire sizes and such go here http://www.miata.net/garage/tirecalc.html , then go to tirerack.com to see what brands of tires are available in those sizes. Hope this helps. Just my worth, those particular cars look good when the wheelwell is visually filled up with tire. I would even consider putting a 235/70-15 on the rear which would still look nice but would be 28" tall & not rub at all.