There is always confusion surrounding the needle & seat on a Holley 2300, or one of the 4 barrels. Here is some explanation that may help clear up some questions.
One problem we run into is carburetors that have been re-manufactured, or customized. They may have had the float bowl switched, or perhaps the needle & seat modified.
Be careful when buying a carburetor kit. Many companies group carburetor numbers too generically and you end up with the wrong needle & seat. For example R-1850, R-1850-1, R-1850-2, R-1850-3, R-1850-4, R-1850-5, R-1850-6, R-1850-7, R-1850-8 all use the 3 piece type as in the 2nd row below.R-1850-9 & R-1850-10 use the type of needle & seat in the 3rd row (short one).As you can see the revision number attached to the LIST number can make a big difference.