For the purpose of developing implementation plans for any interstate air quality control region designated pursuant to section 7407 of this title or of implementing section 7506a of this title (relating to control of interstate air pollution) or section 7511c of this title (relating to control of interstate ozone pollution), the Administrator is authorized to pay, for two years, up to 100 per centum of the air quality planning program costs of any commission established under section 7506a of this title (relating to control of interstate air pollution) or section 7511c of this title (relating to control of interstate ozone pollution) or any agency designated by the Governors of the affected States, which agency shall be capable of recommending to the Governors plans for implementation of national primary and secondary ambient air quality standards and shall include representation from the States and appropriate political subdivisions within the air quality control region. After the initial two-year period the Administrator is authorized to make grants to such agency or such commission in an amount up to three-fifths of the air quality implementation program costs of such agency or commission.