Just depends what you're trying to do and how much you want to spend. For a car that is going to see street miles I'd stay with factory parts since they are heavier and more robust. Plus, you can find replacements at any auto parts store. So for a street/strip car with 15 inch rims I'd use factory knuckles from a FMJ and 11.75 rotors. To save weight I'd use Wilwood calipers. I prefer the radial mounts but I think you would need to make the brackets yourself.