You may find there are subtle differences in both sets of crankcases. If this isn't so, strip the clutch out and remove the blanking/lock plates bridging the case halves. Make sure you've got all the bolts out. You can then strip the bottom case away from the top. I'm not so sure a kickstart will fit a 'non kickstart' crankcase! Wouldn't it be easier to fit your top end to the kickstarted bottom end?