It is very common.

Non-detergent oil was standard/recommended until the mid-50s. It did not hold particles/etc in suspension. So, when at rest, particles dropped out of the oil into the pan.

Clean it out carefully.

I'd either leave the oil pump alone, or install a new one. Maybe someone (Pre '68 Dave) knows where to find a replacement or a rebuild kit?

It looks like the same oil pump was used from 40-52 on all 216/235 engines?

SEALED POWER 2244140 - about $130 at Rockauto.com ?

Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.