You can use the same fox balljoint. But, when you tighten the nut you'll need a spacer or washers to take up the slack between the nut and spindle. This will get your cotter pin lined up. The sn95 stud is shorter.

 

If he is just swapping the spindles and nothing else, then as the previous poster indicated he will need spacer to get the castle nut to tighten down correctly - the spacer needs to be 0.33" in depth. You can either buy a spacer designed for the job - I think there's some guy on corral.net that is selling them, or you can do what I did, which was to stack 3 washers and that worked fine.
Eventually I swapped the original foxbody ball joints for a set of X2 balljoints from Steeda or Ford (same piece I believe). If you swap the ball joints you will need a spacer (comes with the ball joints) to maintain ride height. With the X2 ball joints, the spacer is not required.