small ball joint or big?

Ok so I want to put disk brakes on all four wheels of my '69 dart. So my question is, should i get the regular small ball joint brakes, or should i upgrade and get the '73 and up spindle for larger ball joint? I know it is probably stronger but it is also costlier!! I am planning for this car to be a street rod with either a 383 or 360 with probably no more then 500 hp, so do i really need the bigger ball joints?