help with parts ID 408

Really it depends, scat sells parts or complete kits, and sometimes they balance (internally) their own kits. Best advice is to take the crank, balancer, flexplate, and one rod/piston assembly (with rings, pin, clips, bolts and bearings) to a good local machinist and have them check the balance on everything. If it’s incorrect and you assemble it, it will vibrate like a pup poopin a peach seed.