Phil363

Bob,
 
I found the fastest way to find the gear ratio is to check the external markings on the differential itself that Plymouthy Adams mentioned above.  
 
I attached my differential photo showing 4.1F that is stamped on a raised area next to the fill plug.  Once I removed the axles and pulled the differential I found the 4.1 gear ratios also stamped on the main gear inside. 
 
The second photo is the 3.73 Differential with markings in the same area on the pumpkin.
 
My 3.73 Diff came off of a 1949 4 Door Windsor.  
 
I also have the same vehicle model as you and I do not have a cover on my rear axle.
 
I think that the Hollander manual shows which differentials interchange between our trucks and late MOPAR car models (Dodge, Plymouth, Chrysler) from the late 40's to early 50's. 
 
Phil