My firm belief is a carb rebuild should include a new needle/seat, you might get by without. Some competition racers claim to replace theirs daily b/c the carb timing is important for the hole shot, I question if that degree of fanaticism is necessary. The rubber tips should not be grooved or torn, else the needle can stick in the seat or leak, the rubber tip is impregnated with a lubricant that wears off over time (some tips are red silicone and it's easy to see when the black coating is worn off).
Make sure to obtain the correct sized seat orifice, of course, and reuse your original factory metering arm springs if they're not damaged or modified(to avoid installing the wrong spring rate), most likely the pop-off will still be correct if you keep the original springs. Prior to installing the diaphragm, confirm the pop-off pressure is at spec else if not you'll never get the carb tuned right.
Aftermarket air induction/flame arrestors will change the air/fuel calibration and you'll have to compensate accordingly, temporarily running without an air box can cause a lean condition under heavy throttle possibly leading to piston damage.
