Well, some of them (not sure of the year changeover) had a choke well that was open to the exhaust crossover, and you had to use those little metal "bathtub" inserts with a gasket to seal them up.
They were a PITA, as the gaskets would burn out or the insert would get a rust hole and you'd be pulling your hair out trying to figure out where that da** exhaust leak was coming from... who thinks to look next to the carb?
At some point they enclosed the choke well, and the insert was no longer needed. And eventually they went to the late "open sided" choke.