Your frame will be fine. There is minimal difference between the two. 531st tubesets had forks and stays that were more oval in cross section to provide a more comfortable ride whilst in the 531c tubeset, the forks and stays were more rounded for a stiffer ride. The steel was the same. In fact, there was only one 531 for many, many years.
Your frame will be fine. There is minimal difference between the two. 531st tubesets had forks and stays that were more oval in cross section to provide a more comfortable ride whilst in the 531c tubeset, the forks and stays were more rounded for a stiffer ride. The steel was the same. In fact, there was only one 531 for many, many years.