You can fill those holes with Belzona 1111. It holds all race and alcohol based fuels, including methanol.
The bottom of your float chamber looks like it has corroded, maybe those holes are not casting flaws.
Some of the race fuels have corrosive properties due to their additives, we were recommended to drain the
float chambers every time before longer storage. Carbs were also lubed thoroughly with WD40 or a similar
protective lubricant and we flushed the whole fuel system including pumps with fresh gasoil or diesel.
X 2, Belzona 1111 is your friend