Nothing at all, unless you run a 2 piece style AL or simulated 2pc wheel it'll be 1.5 to 1.75 thru the hole, the nhra wants the 3" stud because they think people use acorn nuts on that style wheel and on a 2" stud there is hardly any thread/nut contact.
If you aren't using that style wheel then you don't need the 3" stud
