That far back and a Cadillac, try the reference section of your local library, sometimes you get lucky and some old shop manuals will be on EBay.
You can also try Faxon Auto Literature in Riverside, California for a factory shop manual. They have a website. Dealing with door latches you may want a copy of the 1957 Fisher Body Manual as well. HTH. -Jim
Search Cadillac Fleetwood Questions
Cadillac Fleetwood Experts
Related Models For Sale