[Sirrotica]

The 64 blocks had the starter provision, but it was only used on stick shift cars, and turbine 300 2 speed automatic A body cars. The 64 B bodies were still 4 speed hydra-matics and slim jims, for automatics. 64 stick cars had an new aluminum bell housing, (previous bell housings were cast iron), and a new flywheel that required the block mounted starter. The 2 speed GTO/Tempest/Lemans also required a block mounted starter, but only were used in A bodies. The B bodies still used a bell housing mounted starter on automatics.

The TH 400 first appeared on 65 B bodies, and on 67 GTOs for the first year in an A body.

I also have never seen any 64 blocks that weren't drilled for block mounted starters, and I've seen quite a few in the last 55, plus years that I've made a living turning wrenches.

I believe standardizing the block for the provision to use either mounting was a money saving thought that all the blocks. One machining operation could be used for all cars, no matter if they needed a bell housing starter, or a block mounted starter. 64 was he final year for the B body automatics requiring a bell housing mounted starter, before switching to the TH 400 in 65. 64 was a changeover year, that fit both applications.