The student pilot reported that, during the landing roll, the airplane encountered a right crosswind gust, and the right wing lifted. He added that "the airplane sidestepped to the left and the left main landing gear wheel assembly separated, and the left-wing tip struck the ground." The left main landing gear strut contacted the runway surface, and the airplane skidded to a stop. The airplane sustained substantial damage to the left main landing gear attachment points. The METAR at the accident airport reported that, about the time of the accident, the wind was from 180° at 6 knots. The student landed the airplane on runway 13. The student reported that there were no mechanical malfunctions or failures with the airplane that would have precluded normal operation. Photographs taken by the pilot during a postaccident examination revealed that an extension casting, which was part of the tailwheel conversion kit, failed where the two lower landing gear strut attachment bolts connect to the extension casting.