I disagree. Unfortunately, there is a LOT of variation in the overall height of the needle and seat assembly from kit mfgr to kit mfgr, and sometimes even from the same source.
However, that said, it still does not mean you need special service tools. What you need is to
a. pay attention that your float was set at the proper height before you disassembled your carb [i.e. fuel level in the middle of the window.
b. note the distance from the float to the air horn with the horn inverted BEFORE you disassemble the carb.
c. adjust the tabs on the float with the new needle and seat assembly to achieve the same distance while incorporating the appropriate gap between the float tab and the needle.
Best
Mark A.