Those are a really rare sight here , i have seen one red 924 recently but that was LHD i would assume it was illegal earlier and was registered through amnesty scheme. Even if you find a subaru or porsche engine in the scrap yards here it would be in really bad condition and spare parts availability is close to none. My personal advice to you would be if you love Porsches go for a later model with the appropriate engine like a Carrera or even a Boxter they are not too expensive in UK and would be a better package overall.
I did not quite follow on what you really want to do
Do you want to keep that car in pakistan or just visit and get a swap done and then drive it back?
Those engines you are talking about are not known here , japanese units are popular here like 2JZ , 3SGTE , 4EFTE SR20DET and other Honda units
There are skilled mechanics but the majority are just the ones that cut corners on swaps , which is dangerous. So you need the right person for the right car