ratio calculator to be used by a shop that makes/sells ratio adapters

I always use the one at the bottom of that page.

There are speedometer companies that make the adapter to your spec/need.

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.