The Olympian was an early 1980s model, also known as the K-8. In 1985 it was replaced by the KHS John Howard Olympian, but yours is from the earlier vintage. Campagnolo Gran Sport components correct. Yes, the tubing is Reynolds 531, but it may not be the full tubeset. The 1984 specs that I have indicate that only the three main tubes were 531. The original price, in 1984, was $600 US
Campagnolo had open format dates codes on the rear derailleur, crankset and hub locknuts of their Nuovo and Super Record components, but I'm not sure about Gran Sport. There may be a two digit patent date on the rear derailleur, a two digit CAM date on the back of the hub locknuts and a single digit year indicator within a circle (indicating 1980s) on the back of the crankarms. Usually, component manufacuring dates are less than two years older than the frame. This may help in narrowing down the model year.
Nice bicycle and what a great deal!