Count the number of head bolts.

http://1954advance-design.com/Stovebolt-engine/head-bolt.html

All of the 216s and the early 235s had 15 head-bolts; and, the later 235s and all 261s had 18 head-bolts.

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.