try this is works with the last one we had.
Take the slobbers from the cats mouth and rub it all over the dogs nose and front, then do the same with the dog slobbers to the cat. Just keep it up for about a week and the two scents with be as one to both.
I'll tell you a story of my friends dog and cats dealings. He had a black crocker and a kitten. the kitten would beat the black dog up, but crockers are that way. As they got older the crocker died and the cat was left alone, my friend went to the pound and got a black crocker that looked so much like his last dog it was uncanny, he let the dog loose in the garage for the first time after getting him home from the pound and the dog and cat were face to face for the first time, they just stared at each other and then the cat walked up to him and licked his face . the cat must of thought that he was the first dog and from that night on they slept together until the cat died 5 years later..