Engine vibration

I once built a 360 about forty years ago and it ran rough but very fast. At my next pull down I took it to the engine balancer and he said it was in balance. I commented the it was not smooth and after looking over the pistons he said the piston heights were all over the place and an uneven power level and compression would cause more vibrations that an out of balance engine. I rectified the piston heights and put the engine back together and it became smooth a silk again!