Neutral balancing a 360?

I've seen one that was internally balanced. It had the counter weights on the crank cut down a little and the throws turned to run 6.125 SBC Scat rods. It had off the shelf .030 pistons for some kind of SBC. I think it got just a small amount of Mallory metal, but it was smooth as silk when it ran. Had a set of iron Seedblaster Magnum heads with an Edelbrock Performer RPM intake. I watched it make 388 HP with a nice torque curve.....thru crappy Magnum exhaust manifolds! It went into a 74 Power Wagon....lol.