NASA's selection of Morton Thiokol Inc. for the contract to build space shuttle rocket boosters was proper and showed no signs of conflict of interest, a Government Accounting Office report said. But Sen. Albert Gore Jr., (D-Tenn.), who requested the GAO probe, said he still has questions about the contract award. The conflict of interest issue was raised because NASA Administrator James C. Fletcher, who was the agency's chief when the contract was awarded in 1973, had served on a board that promoted business in Utah. Morton Thiokol's rocket production facility is based at Brigham City, Utah. Critics also charged that two officials on the NASA board that made the final contract recommendation were former Thiokol employees. A solid propellant booster rocket built by Thiokol triggered the 1986 Challenger accident that killed seven crew members.