Huangpu is questionable. The 054A are built in an indoor shed and that's not going to fit a 055. The ship has to be moved with a mobile dock to the water and that's not going to fit a 055 either. Its far more certain they would be employed to build new batch of 054A+ (AG?) and 054B.
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Guangchan maybe but you may have to make a sizable investment in the tooling and not just training the personnel. The 055 requires a special press to roll steel sheets for the special geometry of the hull. The machine was specifically built for making the 055 but can be adapted to building other ships. We don't know if Guangchan has this machine along with others. It isn't just the dock, but you need the factories to build the modules. Then finally you need the technicians that can fit the equipment. If you want other shipyards to build 055, the day to start training these personnel and incorporating all these machines should have been yesterday. Otherwise you are going to need some lead time in preparing the machines and tools, and training the personnel. After that, you have to produce one or two ships, and subject that to quality inspection, which can be used to adjust the building process. The fact that Guangchan has built the 901 ship gives some confidence of the quality the shipyard can produce but it would be better a step ahead if they have previously built a destroyer.
Circled in second image is the new facility of Huangpu for frigate, and possible for destroyers.