3.90 rear end
1:1 top gear ratio
What tire rolling diameter?
With that number, we can calculate RPMs.

Probably most efficient/mpg at 2500-2800?
Cruising at 3000-3200 would not hurt your engine, but gas milage will start suggering/lower/\.

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.