Welcome to FYI.  I'm sure you will enjoy it and find lots of new friends here, all eager to help another Mustanger.

The key to making a wheel and tire fit is to get the correct backspacing on the 15x7 wheel.  The older style Torque Thrust wheels in that size have only 3-3/4" backspacing, which doesn't really fit well with ANY size tire.  You need to get wheels with 4" to 4-3/8" backspacing to fit the car properly, and that will open up more whel options for you. Click the RIDEHEIGHT link atop this page to see Arjan's coupe that has TT wheels on it.

I used to have 15x7 wheels on my car and I have used 215x60 tires and 225x60 tires on it.  Both required the fender lip to be rolled, but it is a good idea to do that with whatever tire you install.  You might want to consider the reproduction 68 Shelby 10 spoke wheels that have a 15x7 with 4-3/8" backspacing.  I had those on a 65 fastback once.  My daughter's 65 coupe had 15x7 wheels with 4" backspacing and 215x65R15 tires on it.  They did not rub.  That car is also on the ride height page.

Another thing to consider is using a 16" TT wheel.  You can fit a 16x7 on that car easily with just as tall a tire, but having less sidewall bulge so they fit better.

And yet another consideration, since you are just getting started on the Mustang...  If you commit to an expensive set of wheels before the rest of the car is done, you may decide later to install larger, more effective brakes on the car that require larger wheels.  Just be sure you have a plan that details what you will be doing on the entire car before you start spending money on big buck items.