65 cuda slant six timing

mcnoople said
... Later crankshaft had a larger diameter hole which allow the 65 torque convertor to float instead being centered. ...

True. I think the year of change was 1968. The OP can check the pad on the top of the block behind the alternator bracket to find the year. If no stamp, it is likely a dealer warranty block. Charrlie_S here sells the adapter ring.