Don't worry about turns, think in kV. kV tells you the motor's unloaded rpm per volt applied. So...

1000kV on 10V means 1000*10 = 10,000rpm

Nomimally, you want your motor's rpm to be approximately between 27k - 37k (slightly lower or higher is fine), with about 30k being the ideal point. Spinning faster consumes more current which means less runtime.

What motor you need depends on how heavy your 1/5 buggy is. The more weight, the larger motor you'll need (as size is representative of torque, given other design attributes remain the same).

You will not likely reach 60mph. At those speeds, a 1/5 scale can be deadly. To reach higher top speeds, you should ideally get a large, low-kV motor and run higher voltage. This reduces the current consumption which lowers heat and increases runtime.

Hobbyking has some really big brushless motors (you'll know which ones they are when you see the pics of someone's hand holding them and they're bigger than the hand). You'll need to find an ESC that can handle around 12s (LiPo). What you want is going to be tough, and probably pretty pricey.

If you're ok with lower speeds (40mph), that's much easier and the brushless setup is easier to find.