External Balanced 360 With new parts still Balanced??

I know years ago my buddy would swap in any crank that was handy at the time into any 273/318/340 and didn’t seem to have a balance/vibration problem. I took a 340 to the machine shop along with a 318 crank and it was way out, not even close. Would of needed at least 2 sticks of Mallory metal to balance it. Kim