I just rebuilt my from suspension and changed to poly, but these two bushes were like new, still protected by the cover and the rubber grease seals so I just cleaned them up, regreased them and left them.
Having said that If I had of changed them I would have refitted the rubber grease seals and the covers if I could - use the grease that comes with the poly bushes. My reasoning is it has got to help stop ingress of road grit, dirt and moisture that will help even poly bushes deteriorate. This assumes they will still fit and the poly bush is not too wide. Given the position of these bushes they are very exposed, which I assume is why the covers were fitted in the first place.
Roger
1975 Sprint Man O/D in Honeysuckle Yellow
1971 Stag Auto White