small ball joint vs big small joint

The "big ball joints" will not fit the "small ball joints" spindles. Most people change out the upper control arms to the Large ball joint to accommodate the swap to a Big bolt pattern wheel, and late model disc brakes. The difference being the tapered shaft that goes into the spindle. And the ball joint itself is bigger so you cannot just unscrew and replace with a different size. And it is best to mount control arms in the car and then unscrew them with the correct socket and a LONG breaker bar. Trust me on that, no way to hold in a vice that is as good.