IMO it's a good idea to fit poly bushes here if only because the ones available now are generally very poor quality, no where near as good as the Volvo originals. Even those could be past their best after 20k even if they weren't changed until 80k. They are small and take a lot of stress.
Anti roll bar support bushes and end links also a good place to fit poly, very easy change over, but NVH does get affected if you fit them everywhere else. NVH wasn't an exact science back in the 60's.