Patents expired long ago. The designs could've very well been purchased by the Chinese manufacturers. Most of your car parts today are manufactured in China or India due to the many barriers the US has put in place for domestic manufacturing. I understand where you're coming from but quite often the facts don't support the "China steals everything" argument. The real truth is US manufacturers gave most of it away.
Just for quick bit of info, I work in manufacturing, & a lot of our low tech customers, which these carburetors are, in a wide range of industries happily ran overseas to get their stuff made a lot cheaper & increase their profit margins. Fortunately there's still plenty of high precision, high tech, quick turn around demand for our stuff and we're still cranking it out. As much as I hate to say it, the "Buy American" argument was really pretty much ended by the very American companies it was intended to benefit. We used to make stuff for Moog, all gone to India now. We used to make stuff for Tenneco Automotive, all gone to India & China.