rebuilding a khyber engine is no big deal. 100% genuine parts are available, trick is about supervising the assembly of engine no matter how 'experienced ' ustaad claims to be.
try to understand the risk of swap.
yard engines does not have any track record for how long its been there, how much beating it has taken in what type of vehicle. Not every engine is taken out from same variant of vehicle.
SWAP is recommended by mechanics for ease of job at your financial cost, it is a common saying by scrap dealer & mechanics carries deep insult towards person spending money
چلا تو چاند تک نہ چلا تو شام تک آپ سوچ لو بھی ادھر چیک کرو آگے آپ جانو آپ کا مستری جانے
it is your money you need to do some home work, goto suzuki pickup stands and ask about machinist and mechanics they recommend visit those places check out workmanship and decide.
SWAP - is high risk like locating a black cat in dark alley with a blindfold, it involves money and registration book alterations
your money your call your choice cheers !