Just the same as the stockers--place them at the end of the front brake lines!!
OK, OK... You have to find the piston diameters for all the pistons in the calipers you want to use. Use those to calculate the total area. (Or you can just square each piston bore measurement, then add all those together--which is very different than adding and then squaring!) Compare that to the same kind of numbers from the stock system.
If you're not willing to do that kind of math, then use 911 brakes and the 911's 19mm MC.
--DD