I did the 460 swap in my 63 lincoln covertible.
Yes you will need to box the frame and create mounts. You will also need to refab the tunnel for the C6. I rolled my fire wall and set up to tuck all of my wiring behind the fenders. We moved the engine back 6 inches put a full race radiator with double electric fans. I belive the car handles a bit better but I really did not drive the car much before I started the exchange. My 460 is a 92 with a mild build 500 HP. At the time I was just trying to create a more reliable daily driver. I started it 4 years ago so I added a new Holly commander throttle body fuel injection. It really has not worked so well because it required way to much programing. It was just before the good plug & play units that are out now. I am currently replacing it with a carburator. This swap is not an easy or cheap process and few people have pulled it off. This is why many people talk about it but few pull it off. Just a side note I just saw the movie Hit & Run last night where Dax Shepard drives his 67 Continental with a 700 horse power motor in a car chase. The car is his daily driver. I was pretty impressive to see a 6000 pound car ripping around. It was pretty sweet. If you want more info call me Bruce at 530-409-5178.