1963 was the last year for the Dynaflow. You can bolt a '64-'66 ST400 trans to a '57-'63 engine using a adapter, but you can't bolt a '64-'66 engine to a Dynaflow without having the end of the crankshaft machined larger. You could also swap the engine/trans from the '65 and get a better trans.
http://www.ebay.com/itm/Buick-nailhe...item1e6d478c29
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