Do you mean getting it turned 10/10? No, though I am assuming you might be talking about balancing a crank using mallory metal. If you are talking about getting the rotating assembly balanced (I.E. matching the weight of the rods with the new pistons), then you don't have to do that either, though it is good if you can.
If you use the original pistons and rods in the original locations, then you should not need to balance the rotating assembly because you "cut" the crank. If you use different pistons or rods, then you should balance the rotating assembly.
sorry i wasn't clear yeah im talking about having it turned .010/.010. i had the motor out and figured id replace the bearings as its cheap and the oil press was a little on the low side. i found it needs more than just bearings but i'm trying to avoid taking apart the ythe infoop of the motor. so all the roatating mass items will be the same. i didn't changing .010 of steel for .010 of bearing material wpoul;d make too much difference but wanted to hear some other opinons.
thanks for