By the middle of 1960, all of the then-current length of SR 166 was paved. By 1966, the limited-access portion of SR 166 was under construction from I-285 to US 19/US 41/SR 3. Later that year, the construction was complete along that section. In 1967. the extension of SR 70 was renumbered as part of SR 70. In 1969, the limited access portion was proposed to be extended from its current eastern terminus, at Lakewood Avenue, past SR 54 and McDonough Boulevard (today's SR 42 Spur) to end at a proposed piece of SR 400.