FHP, a Fountain Valley-based health maintainence organization, completed its conversion to for-profit status Nov. 26, following negotiations with the state and a court ruling upholding the purchase of the HMO by its management . . . The Treasury Department's regular auction of short-term Treasury securities was postponed this week because of congressional failure to pass legislation raising the debt limit . . . The J. A. Frates group said it has increased its total potential holdings in Kaiser Aluminum & Chemical to 10.48% from the previous total of 9% . . . Valley Grain Marketing Inc., a Sonoma County-based firm that stores and sells grain and seed filed for protection under Chapter 11 . . . Atlantic Richfield said it completed the sale of its American Brass division to a group of investors.