Blast from the past...Convair Kingfish.

via Wikipedia...

KINGFISH
After cancellation of the B-58B in mid-1959, Convair turned to a completely new design, similar to their earlier entry in name only. The new "Kingfish" design had much in common with the Convair F-106 Delta Dart, using a classic delta wing layout like most of Convair's products. It differed in having two of the J58 engines buried in the rear fuselage, and twin vertical surfaces at the rear. The intakes and exhausts were arranged to reduce radar cross section, and the entire aircraft had the same sort of angular appearance as the later Lockheed F-117. The leading edges of the wings and intakes continued to use pyroceram, while other portions used a variety of materials selected for low radar reflection, including fiberglass. The new engines reduced the cruise speed to Mach 3.2 compared to the "Fish"'s Mach 4.2, but range was increased to about 3,400 nm (6,300 km).
In August 1959 the teams met again to present their latest designs. Lockheed had produced an aircraft similar to the "Kingfish", the A-11, but it was more "conventional" in layout. Although the A-11 had somewhat better performance than "Kingfish", the panel generally preferred Convair's design due to its much lower RCS. Johnson expressed skepticism of Convair's claimed RCS, and complained that they had given up performance to achieve it: "Convair have promised reduced radar cross section on an airplane the size of A-12. They are doing this, in my view, with total disregard for aerodynamics, inlet and afterburner performance."
In the end it was not performance that decided the outcome; during the U-2 project Lockheed had proven its ability to design advanced aircraft in secret, on-time, and under-budget. In contrast, Convair had massive cost overruns with the B-58 and no secure facility similar to the Skunk Works. Lockheed promised to lower the RCS in a modified version of the A-11 known as the A-12, and that sealed the deal. The A-12 entered service with the CIA in the 1960s, and was slightly modified to become the Air Force's SR-71.

Another tantalizing 'what if' we had gone this way airplane...