If you want to match the original style interior you won’t find any pre-made seat covers. There are plenty of aftermarket sources for the 1964 thru 1972 F-85/Cutlass but really none for the 1961 thru 1963 models. If you have a multi-clored interior it will be even more difficult. I had to have an upholstery shop make new seat covers using my originals as patterns. I purchased the vinyl seat material from SMS Auto Fabrics. They also have door panels for quite a few different cars and may have them for your car. You might want to try contacting them. Their website is smsautofabrics.com. A word of warning though….I had good luck with them 3 years ago but another member of this website had trouble with them. See the thread in this forum titled Upholstery Material. I’m not promoting them by any means but they are the only decent source I’ve found for material. They will send free samples for your review. All you need to do is give them your trim code. This is on the VIN tag located on the firewall near the windshield wiper motor. It will be a 3 number code located between the words “trim” and “paint” on the tag. This code will tell them the style and color of your particular interior. The material I got from them matched perfectly. I was lucky in that my door panels were in good condition but discolored so I dyed them to match the seat material.
Good luck with your project!