Yes, you can. If you had 03 calipers, and 98 spindals, you would have to grind a little bit off of the mounting tab on the brackets...but what you have will bolt right up.
I have a set of 04 PBR 4 piston calipers if you would be interested in trading for your 98 2 piston calipers.
As far as the ball joint goes, you can use your Fox ball joints, you just need something to take up the extra space. Alot of guys will just use a stack of 3 or 4 washers, but there is a guy on another site who makes spacers and sells them for less than $10.