Try to fit a 1000 CC engine into 500 CC bike!! It won't fit.
For that to accomplish you need lot of time, money and structural changes.
This is purely misconception that you can fit any engine to any fighter or can upgrade it with other engines available in open market.
Please understand that the aircraft is designed around a particular engine, like
1. Rafale around M-88 series whose dimension are similar to GE-404, that is why during development phase when M-88 was not ready they used GE-404.
2. JF-17 around WS-13 which is similar to RD-93.
3. Tejas around Kaveri, which is similar to GE-404.
Note: I said similar, it means comparable weight, dimensions, thrust and various other important attachments.
If you want to upgrade the engine in any fighter then you have basically 2 options:
1. Easy way: Ask the original manufacturer of the engine( engine which is currently fitted) to improve the engine in terms of thrust or whatever parameters you want, so as not to change the overall shape, size and attachments. Still you will need years for testing and some modifications, mind it those modifications are small but not easy.
2. Hard way: Change the engine available from open source. Go for many complex and time consuming structural modifications including various other auxiliary units. This will take more than 4-5 years and also much more expensive.