Rubberneckin' was originally on the Don't Cry Daddy single that reached no. 6 on the Billboard Singles chart in the US on 12/13/1969. This is interesting to note: Billboard lists it as a double A side single. This makes the highest chart position for Rubberneckin' at no. 6 in 1969 on its original release. So, technically, Rubberneckin' was a double A side hit.
But... it was unofficially the B side. Recall that The Long And Winding by the Beatles was technically a double A side with For You Blue according to Billboard. But we all know For You Blue was a throwaway B side. This is how Rubberneckin' was regarded even by RCA and BMG.
Otherwise, why wasn't Rubberneckin' on the Elvis Top Ten Hits album? Also, why wasn't For You Blue on Beatles 1? But nevertheless technically Rubberneckin' was a double A side in 1969 ...