1954-1957 USA 261 truck engines use a by-pass oil filter
1958-1963 USA 261 truck engines use a full-flow oil filter
All USA 261 engines had mechanical (solid) lifters

All Canadian 261 engines (car/Pontiac and truck) use a by-pass oil filter (all years)
All Canadian car/Pontiac 261 engines had hydraulic lifters.

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.