BY STEVE LACKMEYER Business Writer slackmeyer@oklahoman.comDevelopers of First National Center are preparing to start conversion of two-thirds of the building into a 680-space garage in September as negotiations advance with Oklahoma City for tax increment financing assistance. The parking is part of a $230 million redevelopment that would convert the original 1931 Art Deco tower into housing and a hotel, while the 1957 and 1972 additions built to the east of the tower will be converted into a garage with retail on the ground floor. The Oklahoma City Economic Development Trust unanimously approved a memorandum of agreement that would allow for a $15.9 million loan to be obtained by Cornerstone Development CEO Gary Brooks and his partner Charlie Nicholas. The loan would be issued within 180 days of completion of the garage.Read more on NewsOK.com