Thanks for the info, I will keep on with my quest.

If you know the original buildeers, it may be possible that they have plans for the launch, alternatively, if it was operated by the PLA, then you may be lucky there, otherwise, the only suggestion that I can make is the National Maritime Museum at Greenwich, they would definitely have the originaal plans. How costly they will be, I do not know, but certinly try the PLA as a first port of call, if no luck have a look for the original builders.

Happy Hunting