actually instead of longer ball studs you should just use the ball studs that let you add the screw through them so you can get the length just right...such as these....
http://cgi.ebay.com/3Racing-4-8MM-HE...item27b159d861
The only reason I suggest those is because you will have the rest of the threading sticking out the front of your tower if you get the longer ball studs Carno suggested. With these though you get the right length screw and the ball stud acts like the nut and it looks cleaner.
