By the 1945 renumbering, only the sections of SR 206 and SR 70 east of Cocoa were completed. SR 520 was defined to use sections of SR 418, SR 206 and SR 70. It would begin at SR 50 (former SR 22) near Christmas and run southeast along the general alignment of SR 418, switching to SR 206 where its planned alignment crossed. (SR 418 south of that crossing later became SR 532.) From there it would take SR 206 to Merritt Island, and SR 70 the rest of the way to end at SR 1 (former SR 140).