WOuld it be better to get 17" or 18" rims first and new tires or lower the mustang and keep the stock rims for a couple of months???
well if you do it right, your exterior diameter of the tire will be the same. if you don't make sure to do this, your speedo will be really off, and you will have to get it calibrated again.
Here's my guesstimate: 18" Cobra R wheel- $200(stock)/$300(chrome) Tires-$800 Springs-$200 If you want shocks and struts-$150 Labor for all that might be $500. So in the end, you might look at $3000.