Just a FYI
In above POST By tclederman.
The "Classic Parts" link shows the six hole shims/gaskets for Hydra-Matic & Powerglide automatic transmissions.
And also the four hole shims/gaskets for the manual shift transmissions.
Hydra-Matic illustration
Note: Manual shift transmission does not use a ball seat.
Tip: Check for two O-ring oil seal washers in Torque Tube Retainer I had one missing.

1954 Chevrolet 3105 Deluxe Panel Truck
w/Factory HYDRA-MATIC