In 1963-'64 the Impala and the Corvette shared many common parts (the 1953-'62 Corvette was a full size car with the frame shortened where the rear seat would have been and a plastic body dropped over it). Since the 1961 shares parts in common with the 1963-'64 (not all of them unfortunately) so I would think a 1964 Corvette steering knuckle with the then standard Corvette calipers and rotors would bolt right up to your existing ball joints. They may have gone with a bigger ball joint on the Corvette than the full size that the Chevy engineers pulled from a light truck's part bin, but there exists a Chevrolet part that will still interchange.
All GM cars were built from a limited number of parts that interchange to one degree or another (the disc brakes you are looking at come off of a 1969-'72 Chevelle). GM engineers were not allowed to design a new part (Ford's better idea) if there exists another part that can be adapted to fit the application.
This is why you can ask for a water pump gasket for a SBC and it will be the same part from 1955 through 2004 (same water pump casting as well, but they changed the direction of the rotation of the pump in 1986). This is GM corporate policy in effect from October of 1957 forward.
In fact there used to be an unpublished (hidden from public view) parts book that had every GM part number with an interchange so that the cheaper Chevrolet part could be substituted for the same part on a Cadillac that cost three times as much.
There was a time before computers that your Chevrolet service parts counter man knew what parts fit what without ever opening a paper catalog to look it up. I used to know a lot of them in the late sixties but they are all retired now. They could tell you if what I suggest would work or not just from memory.