The rate of compensation for any position under the appropriations now available for, or hereafter made for, expenses of inquiries and investigations of the Senate or expenses of special and select committees of the House of Representatives shall not exceed the rates fixed under chapter 51 and subchapter III of chapter 53 of title 5, for positions with comparable duties; and the salary limitations of $3,600 attached to appropriations heretofore made for expenses of inquiries and investigations of the Senate or for expenses of special and select committees of the House of Representatives are repealed.