3789717 is the 1958-1963 261 block casting code.

Post the head casting code and the head&block date casting codes and you/we will learn more.

Also, please post a photo of the Engine Serial Number (If you have not already done so).

The second and third links in your post above are the same photo.

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.