I've seen originals with mufflers, and I've seen them with the chambered intermediate pipe. They all had the resonators. The ones with mufflers were automatics though. The one I absolutely fell in love with was a '66 Formula S with a 4 speed and the chambered pipe. 44 years later and I can still get wood over the sound of that thing going by the house around 6000 RPM in 3rd gear. Best sounding exhaust ever put on an A body.