[rotorwrench]

The first version of the 78 case was for simpler gear sets. The second version came out in 1939 for use of the new gear set for the Mercury cars plus the new synchro set up. The later changes were due to limitation of resources for the war effort and finally due to outside manufacturers making them for spare parts. That 78 case had a long run from 1937 up into 1951 for production and a few more years for spare parts.