There is a website with PDF Parts and Illustrated Parts catalogs/manuals for 1961-1972 Buicks, though the site says 1940-1972. Wild About Cars Online 1961-1972 Buick Parts and Accessories Catalogs — http://wildaboutcarsonline.com/cgi-bin/pub9990334158924.cgi?categoryid=9990334161791 Each manual is downloadable as PDF's. I downloaded each and saved to a CD for future access in case this site ever disappears. Can I recommend pinning this thread for quick reference?
WildAboutCars went to a new website at: https://autohistorypreservationsociety.org/factory-documents/ www.65gs.com also has a bunch of great info! For the parts books, go to the 'Documentation' tab. https://65gs.com/