old school balancing job....
First and formost a VERY GOOD scale...weight all 8 pistons...grind material off the skirt on each piston heaver than the lighest one to match the lightest piston's weight then do the same thing to the rods..weigh all 8 rods and find the lightest then grind off material on the 7 heaver rods. Taking a small amount off the skirt and off the rod's will balance the parts to each other...is that what your talking about?? Its a lot easier to do with motorcycles.....I have done it on my drag bikes...it works! Then you should balance the rotating assembly...only a engine shop can do that for you.
Rat Rods Rule!