It is unlikely, but altogether possible for this "high idle/surge" to be something else.
It may NOT be the carbs at all. It could possibly be the breaker plate in the distributor is hanging up or the advance spring(s) is shot or missing. That would do it as well. It's also possible that the distributor turned a bit, and idle advance is higher than it's supposed to be. This would increase the speed, enough to be getting into the advance curve which adds even more advance. Throttle plate closed, eventually the engine starves a bit and the speed slows.
90% of carburetor problems actually ARE ignition problems. Check there first before messing with carbs, other than verifying throttle return/linkage sticky-ness.