Big problem first off is the Impala spindles are taller than the Nova spindle. You will have to relocate the upper control arm to get the right geometry. Moog has a catalog and if you can get to a good parts store they might have one. Back of the book there are listings for each ball joint number and will give you the pin height, width and taper. That is the best way to find out with out buying a ball joint. You can also just go to the parts store and have them pull them both to inspect.
If I can recall they are different but could be changed out with a little fab work. Why do you want to change them?