Engine running away after carb rebuild....

Check the throttle linkage. Changing carbs, did you get something backwards? Where is the throttle stop when it's racing?

My 64 has the old style linkage (rotating tube/bellcrank, not a cable) and one time I hooked if up incorrectly and it went full throttle right away.
It sounded like this:
RRR-RRR WHAAAAHHH!