I didn't bother to look up the venturi sizing of the 263, but I offer a tip for all. Using a carb too large for an engine will make it impossible to tune one end or the other. You'll be able to get one side, but never the second. A carb that would fit the 30 would not likely have a venturi larger than 13.5mm-14mm. That's stretching it.

Look at the inlet side of your carb. Note the small number stamped onto the inlet. That's the venturi size in 64's of an inch. There are a lot of online conversion charts out there so it's easy to do the math.

Next tip. When you go shopping for a different carb, make sure it has a choke before making the purchase. We've come far enough along not to be sticking our fingers in a carb to choke it. Then again, if using an electric starter a choke isn't necessary. Just takes longer to get the fuel going. I just love spinning a cold engine for up to a minute for the first start of the day. Very little oil remaining from the last time it was run and you're spinning at a couple thousand rpm for a relatively long period.