Market has plenty of kabuli engines of cuore. these are EF-EL 660cc EFi and ED-20 850cc EFi. local cuore has ED-10 850cc carby.
both EF-EL and ED-20 are more powerful than local cuore's engine. all have same blocks but different heads.
local cuore's engine is not available in used parts. if it will be, it will be a stolen one most probably.
last year i found that 660cc engine with uncut wiring was priced 25K and 850 at 30K in my city sahiwal. shop keeper gave guaranty that engine is in good condition. you will have to pay labor extra for fitting. it is bolt on swap.
anyway my cuore has done almost 130K km and is running strong. what are the problems you are facing? maybe changing rings and pistons and head job will make engine good for 100K km more.
finding good second hand engine is not easy. some senior member can guide you.