The SPACER you are wondering about (was separate on 1954 EBU 239CI) was incorporated into the harmonic balancer assy for 1955/ production.
If for some strange reason the engine has an early 239CI balancer, GOOGLE B4AZ 6359-A for the Service Replacement.
The spacer is part of the balancer. Measure it out to be sure of what you have.
The balancer will have the spacer built in. When the balancer is installed, the slinger will be pressed tightly against the crank driven gear (6306). See where the incorporated spacer in the below photo shows wear from the front seal?
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