Most of the early year 500/550 carbs are somewhat interchangeable. Say up to ‘76 possibly depending upon the market you’re in. You do want to avoid “PD” model carbs as they are rather different than yours likely are.
There is a member here in the States, Jim French, who offers a laser-based micro welding service to rebuild and repair those float posts. His fees are very reasonable, though I’m sure shipping would be the bulk of the bill.