Timing Chain Cover crankshaft opening is the wrong size

Cast crank engines need to use their correct balancer, a weight kit needs to be installed, or a complete engine rebalance to swap internal and external balancers.
But only with the cast crank 340/360 engines, which each had their own unique balancer. 318s were all internally balanced regardless of whether they were cast or forged crank, and used the same balancer 9with the timing mark and bolt hole differences already noted).