Some basics. Smaller bore size equals more line pressure. Suggested MC size, 1inch to rear, 7/8 inch to rear. Use the shortest, braided brake lines from the hard lines to the calipers as possible. Use a bias adjuster-easy with a dual MC system. Have 100lbs more pressure to front than rear. Adjust from here. You do not want the rear to lock up before the front. I use a gauge that is hard plumbed in the system to know pressures for sure. An inline dual piston MC will require a bias valve. A lot of kit cars don't use any bias valve. Big mistake. And when they do most are from a donor car which in most cases will not be set up properly for the weight and bias of a Cobra.
One of the biggest mistakes is to not bed in the brakes properly from the start. Make sure all of the protective
oil has been removed from the rotors to start with. With new brakes go out and at 40 - 50 mph hit the brakes hard, bring the car to a stop-just short of locking them up. Do this 5-6 times. You should smell the pads. Bring the car in and let it cool completely. The purpose of this is to bed the pad particles into the rotors. If you don't do this from the start the brakes will never be as good as they can be.
I have floor mounted pedals which generally have a lower leverage ratio than hanging pedals. I have no problem locking the fronts. I run 275/18s.
Also, if your MCs are floor mounted and are lower than the calipers, you will want to use residual valves. These keep the fluid from draining out of the MC. if this happens your pedal will have a lot of travel before they move enough fluid to fill the calipers back up. Install the residual valves as close to the MC as possible. 2# valves for disc brakes, 10# for drum brakes.
Good brakes are a must. It's worth the time and effort to get them sorted out. Good luck.