the question is how many Al-31s have been sold before 2016 and how many Flankers have been sold by Russia?
Do your sums and math, according to Russian media China bought 1000 Al-31s up to 2013
So i am asking you how many times you can re-engine the Russian made Flankers? how many J-10s you can build and re-engine, the math will tell you this, 1000+100, means you can re-engine 4 times the Flannker Chinese fleet or 2 times the Flanker fleet and at least 1 time 300 J-10s, make your numbers.
Remember these are spares the Flankers built in Russia had its own Al-31, no need to buy spares, also you are claiming WS-10 is very reliable, thus no Chinese J-11B or what ever clone after J-11s use it
Ahem J-16.