I may be off here, and since I wasn't sure I didn't want to chime in. Buick switched to a twin-turbine dynaflow in '53, ad '53 was the last year of the straight eight...I BELIEVE that the earlier Dynaflow will not bolt up with the '53 engine. Go to buicks.net and post in the straught 8 section...if I'm wrong, someone there might know. Good luck!
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1953 Buick Special Riviera 45R
1965 Buick Skylark 44437 300-4V
1965 Ford Mustang
1965 Chevy Corvair Monza Convertible