Off hand, here is what I know. If I can find more information before this question closes, I will edit.
I know that Elvis was an 8th degree black belt. However, even though he earned and completely deserves the rank of 8th degree black belt, I think some of the black belt ranks are honorary. As for the cape, it has been returned to Graceland. It is now displayed in the Raquetball Court with the American Eagle Jumpsuit. The guy that caught it, willed it back to Graceland after he died. As far as I know, the belt is still MIA.
Elvis #1's from the 70's are:
Suspicious Minds - my mistake, this song was #1 in 1969
The Wonder Of You
Burning Love
Way Down
Here is some information I found about Elvis' black belts. According to this website: http://members.tripod.com/beyondthereef__1/tigerman.html
Elvis was a quick learner. According to Elvis, he was awarded the 2nd degree in 1963, skipped the third degree, was awarded 4th sometime in the 60s, 5th in 1971, 6th in early 1973, and eighth in August 1974 (Ed Parker insisted it was an honorary degree). Elvis told Ed Parker (and anybody else who would listen to his boosting of martial arts) that, had he not been involved in entertainment as he was, he would have loved to have been involved full-time in the martial arts, training and teaching.