haey man !
wenevr u make deal, do it on stamp paper as tht is most legal way,i m also selling my leased alto and hav sold mehran, and no problem is expirienced alhamdulillah ... han be sure tht no installment is short till ur deal is mature and done...
now as i m selling my car, i'll tranfer cars right to him and tht will be written on stamp paper,bank has no intrest either u r paying instalment or some other person,bank only need installments...