Depending on the porting, you can still use stock carbs with a ported engine but you might not be getting the full power the engine is capable of.
You do not need bigger carbs now but you would notice better throttle response with 28mm or 30mm Keihin PWK carbs - don't go any bigger without porting.
Alot of people like the 2 into 1 single carb set up with a 33mm-35mm carb - they claim a gain in bottom end power