A few things on Coe:
It's hard to determine how Coe would have run ina 5k based off ANY of his performances. If he trained for the 5k, he would have to completely shift the speed of the intervals done in his 5-pace training. While workouts would probably be similar, the speed and thus effects on the body physiologically would be very, very different.
I don't know if this is 100% true for sure, but I can say that Jim Spivey, who was coached by Dr. David Martin )who worked with Peter Coe), said inconsistencies in his racing, i.e. not making the 1988 olympic team a year after his bronze at the WC, were due to the fact that he was soley focusing for the end of the season, around august. That year, despite not making the team, Jim ran 3:31.01, 2nd fastest time by an american ever. I would think it would be the same with Coe, as despite some shaky races, he medaled in every championship race he was ever in.