My bet is that he is incorrectly referring to the dippers on 216 engines. The 261 (and 235 truck )engine from 1954 onwards had high a pressure oil system. The earlier truck engines had dippers on the bottom of the connecting rods (and lower oil pressure). Nonetheless, I believe that either engine could have an external, bypass oil filter (canister--style) attached to in intake manifold.

If "slingers" means something else, I am interested in learning about them. (A dipper might become a slinger if it is installed backwards).

Tim