Chevrolet came out with 3 speed overdrive in 1955 so tell us more about your 1941 sedan transmission conversion (torque tube? rear axle ratio?).
Pictures of your transmission and drivetrain?
I assume you wish to keep your column shift and do not wish to convert to floor shift?
What you have now is a manual 3 speed transmission with an added overdrive. The overdrive portion is designed to function automatically (no manual shifting).
Most like the automatic function and I'm surprised you are not happy with it.
