Respect, Snorks that vintage Dellorto is a great carb which will improve performance on the China girl and support aggressive tuning of these engines, like your expansion pipe. I've used these Italian made carbs on both 2 & 4 cycle engines since 1960 the first was on a modified 8 hp Cushman Eagle (a round slide Dellorto) and have used both round and flat slide Dellortos on many projects since. They are really well made. The Chinese SHA clones don't compare by any standard to the new Italian made flat slide Dellorto, except in price and the new Italian made carb doesn't compare to the vintage carb either, except in price. The old ones are hard to find in decent condition though and can cost a lot.
Good find I wish I had a dozen of them just like yours. I'm a fan. Just to show I'm not a hater I have a couple of SHA clone carbs on my 66cc motors that work fine and produce a little performance boost, but nothing like the real Dellortos provide especially when tuned to work with a quality expansion pipe (KTM or Yamaha etc.)
Rick C.