318 balancer on a 360 crank advice needed

Just throwing a thought in here, but have you measured the distance from the pulley mounting surface to the inside flat surface of the hub that the seal rides on and the keyway groove is cut into. See if the 318 and 360 are the same distance, then measure to see if the outside rings are the same distance out. On my engine I use the thick 360 damper with the groove machined into it for counter weight, but the ealy 360 used a thin damper with a counter weight. My from the outside of the ring to the flat part with the 6 holes to bolt the pulley on is recessed deeper than the early 360 damper but the pulley still lineup the same. So I guess what I am saying is maybe the ring on your 318 damper is further out on the hub but the pulley mounting surface is the same. Like I said just a thought.