I never noticed 360 balancers with "scallops" front and back, just the front. But when they changed from the original counterweight cast into the front to the scallop in the front, it was on the opposite side of the face. Basically the offset weight remained the same but they saved the amount of metal used. Are the internal parts OEM rods & pistons or different parts with possibly different weights? 360/5.9 Magnum are externally counterweighted but a lesser amount than a LA 360 and more than a cast crank 340.