Persian Jews were never Sephardim. The Persian (Iranian) Jewish community is the oldest continuous Jewish community having been in existence in present day Eastern Iraq (the city of Susa is Shushan) and Iran since Churban Bayis Rishon.
Jews from that part of the World, Iraq, Iran, the Arabian peninsula are properly called Eastern (Mizrachi) Jews and have their own nusach and minhagim and many are very maqpid on shiduchim. Mashadi Jews (from the Iranian city of Meshad) are reputed to only be meshadach with other Meshadis.