North American submitted a design of it's own in late 1947 which was based on the F-86 with a bifurcated NACA type duct feeding a J48 in the middle, and allowing a new nose with an SCR-720 in it. The engine was equipped with an afterburner, and the wings were the same. The design was fairly easy to submit because it was considered a modification of a design already flying, and was originally called the P-86C/F-86C, and later YF-93 (presumably because they got their way
).
The first design to fly was the XF-88, which flew October 20, 1948; The XF-90 flew next on June 3, 1949; the XF-93 flew last in January, 1950.
The XF-90 might very well have looked the sleekest of all of them: It didn't perform the best, but on the bright side, it was tough. It was actually the only design built to the g-requirements the USAAF/USAF required (12g ultimate load), unfortunately living up to the obligation didn't pay off very well for them -- the aircraft was overweight.
The XF-93's engine inlets proved to be a problem, so it went from the NACA duct, to a pseudo-NACA duct (a term I created to best describe it), to a regular D-inlet. The aircraft was said to have a good rate of climb, and a maximum range of over 2000 nm. It wouldn't shock me if it didn't maneuver so good at high altitude with extra weight on the same wing. The radar was a nice-feature though -- and offered to combine day/night fighter into one design.
The XF-88 won, but for one reason or another it was cancelled...