I am no expert, but I am a big fan of Nebbiolo. From my searches on the net, 1987 was not a good year in Piedmonte. The vintage scored an 83 on a 100 point scale where 1997 scored a 99 and 2000 scored 100. Of recent vintages Piedmonte has had tremendous success with the exception of 2002 which was a washout. On the rating I quoted above it scored an 82. Many wines were not even released in 2002 it was so bad. So with 1987 scoring 83 on that scale I would not be optimistic.
I have no knowledge of the 1955 to help you with.
I am currently purchasing 2001 and 2004 Nebbiolo as they were very good years that should cellar well for 20 - 30 years.