I don't have a 65 parts book, but according to my Galen Govier code books, there were 6 different radiators produced for the 65 B-Body cars. I will list them as they appear in the code book. You should be able to hopefully match a part # to your top radiator tank if you car still has it's original radiator. As far as I can tell, all of the 62-65 B-Body cars were equipped with either 19" or 22" wide radiators, depending on the engine size and if the car came with factory air conditioning or not. Galen does not list the width on all of the 1965 radiators, but I would assume that they are 19" wide unless they are listed as 22" wide. Maybe some other member can fill in that information for you. :dontknow: Hopes this helps you out.
Richard
2524963, 225 /6, manual trans, no a/c
2524966, 273, 318 V-8, manual trans, no a/c
2524968, 273, 318 V-8, auto trans, no a/c
2524969, 273, 318 V-8, manual or auto trans, with a/c or with hi out put alternator
2524970, 22" wide, 361, 383, 426 wedge V-8, manual trans, no a/c
2524972, 22" wide, 361.383, 426 wedge V-8, manual or automatic trans, with or without a/c not listed