The original 55.1 came with a 6 volt system, meaning you will gave to double check if the new starter matches your voltage and existing flywheel. 6 and 12 volt systems came with different flywheels.
Here is a “Tech Tip“ written by Bill Hanlon that explains the difference.
Flywheel and StartersHere is possibly another option, from Chevs of the 40’s.
Starter