I would personally be very concerned about rehoming a cat with any 'sighthound', e.g. Greyhounds, Borzoi, Saluki, Lurchers etc. If they see anything run, they will chase and kill if they can. It is in the breeding going back into their distant history. It isn't the dogs fault, and it may be very different if a kitten and a puppy are brought up together, but in any other circumstance I really wouldn't risk the cats life.
Also most rescue Greyhounds, although lovely, gentle dogs with people, and they are gorgeous natured, are ex-racing dogs and are conditioned to run after a small, fast furry object, even if it is an automated rabbit.