305D Distributor (plastic washer?)

[Clarke]

I just installed a new gasket kit on the engine and transmission, painted them up, and in the process of bolting on all the components. I noticed when I pulled the distributor out there was not a plastic washer in the bottom; however, the kit has one in it.

Is the 305D motor supposed to have a plastic washer at the base of the distributor (where the oil pump shaft inserts), or is it designed to be metal on metal?

Thanks in advance for your feedback.