As the various articles at the links above (and my own link) notes, you will have to manage all interactions and may never have a dog and cat that are happy in each others' presence. If the cat is older and new he will especially need places to escape and time away from the dog. Cats stress out very heavily in a way dogs generally do not hence it tends to be the cat that needs the extra care and precautions not the dog. You cannot rush anything; it is a matter of time. It took months for my two feline girls, Pippa and Jessie, to be OK around Jaspar (the first in my house) and while neither of them were thrilled with the dogs they cohabit fairly happily now and will all share a couch with the dogs (as you can see in my avatar -- the main reason I got a cavalier in the first place was that it is a small breed known for getting along well with cats). The toms both like the dogs -- Quincy adores them so much they consider him a pest as he constan tly wants to rub against them or curl up on them -- and when Ambrose was a kitten they played very actively though now he is more aloof. So it really depends on the cat and the dog. I always would err on the side of protecting the cat and be very cautious though. Especially a declawed cat who now is very at risk and has little way of defending itself -- biting is not a normal defense for a cat and it would have ltitle chance against an attacking dog (which amongst other reasons is why declawing is illegal in Ireland and the UK). Dogs can have their prey instinct kick in by a fleeing cat even when they seem to be best friends so again, always proceed with some caution and manage interactions until you know both cat and dog very well and they know each other very well.
If the cat is at all wary or upset a Feliway plug-in with cat pheromones can really work wonders. Widely available online or from vets.