When I was replacing a frame on a 64, I had a rust problem and couldn't find any good advice on how to convert a later frame to the 64 specs. As I remember, the 82 frame would have to be cut where it goes over the wheel and replaced with sections that would allow you to bolt the rear bumpers on the 65. You can buy pieces of frames from aftermarket suppliers, but it requires quite a bit of work,....and money.
You might be able to shop around and find a good 65-67, or early 68 frame. Patching an 82 frame will undoubtedly devalue the car. I picked my 64 frame up at the Knoxville TN spring show several years ago. Hemmings usually has frames for sale too.
Learn all you can before you buy one, so you know what you are looking at. A 63/64 frame is not the same as a 65. I travelled to Arkansas to look at a "perfect" frame and when diagonally measuring from the body mounts I found it was twisted. The seller said that he had a frame guy look at it and supposedly said it was the best frame he had ever seen.