I asked a similar question a while back...
Friel has a very general chart in his "bible"...from a flawed memory the quality of race-fittness is indicated by excellent, good, average, and poor. Excellent was >4-5min above LT; good, 3-4> above LT...or somewhere around there.
As everyone else has said, however, it depends...asgelle sums it up nicely/informative article if training with power.