Sync'N'Replace Audio

Sync'N'Replace Audio is an application that lets you synchronize video and audio files directly in Finder.

You just need to select some video file and a high-quality audio file, right-click, select "Synchronize", and you'll get a file with the replaced audio. Selecting the shots, right-clicking on them, and firing the extension is all you need to do. In seconds, you'll get a new clip with untouched video and perfectly aligned audio.