In 1964, Fairchild Stratos Corporation proposed a modification of the Convair B-36 Peacemaker for transporting the second stage of the Saturn V, much the way Conroy modified the Boeing Model 377 Stratocruiser into the Pregnant Guppy to carry the third stage of the giant rocket.
Sources:
http://www.456fis.org/XC-99_B-36.htm
http://www.air-and-space.com/b-36%20variants.htm
Sources:
http://www.456fis.org/XC-99_B-36.htm
http://www.air-and-space.com/b-36%20variants.htm