This is a pretty loaded question without knowing what you expect from the car.

I had a Mustang that I ran on the road coarse. It was a 93 with factory 11" discs in front and 10" drum in the rear. Probably will stop better than any factory muscle Mopar with OEM front disc and I was pretty content with them on the street. Until I put it on the Toronto Motorsports Roadcourse. Factory brakes were absolutely cooked after 3 laps. Brake fluid boiled to a point I had no front brakes.
Upgraded to 13" dual piston in the front and 11" rear. The braking power in this 3300lb car was awesome. It could go 10 laps without overheating the brakes. I could notice a slight downgrade after 10 laps but still excellent. I was tired before the brakes were. Then I road in the same car with 13 in all 4 corners. Brakes were supercar level.

After the initial upgrade from drums to small front disc. This will allow for modulation and a big improvement over stock drums but after that it's just how much do you abuse your brakes. All of this does not apply if you run tiny tires.