The Air Force chose Boeing's
MX-1712 and Convair
MX-1626 design studies to proceed to a Phase 1 study. During this period Convair took advantage of recent developments by General Electric and replaced the two large J53 engines with four smaller
J79s optimized for supersonic flight.
[8] The recently formulated
area rule was also applied to the design, resulting in aerodynamic re-profiling and an even more slender fuselage. Having been refined, Convair redesignated their renewed submission
MX-1964.
[9]
In August 1952, Convair's design was judged superior.
[10] According to Gunston and Gilchrist, Boeing's submission was viewed as equally good, but their separate contract to produce the
Boeing B-52 Stratofortress had undoubtedly influenced this competition.
[9] In December 1952, Convair was chosen to meet the new SAB-51 (Supersonic Aircraft Bomber) and SAR-51 (Supersonic Aircraft Reconnaissance) standards, the first General Operational Requirements (GOR) for supersonic bombers. In February 1953, the Air Force issued a contract for Convair's design, designated
B-58 on 10 December 1952.
[11][12]