LL Cool J was absolutely shocked when he found out Bob Dylan just covered one of his most famous rap songs -- but the more interesting part ... LL wants to do a duet with the music icon.

LL Cool J: Click to watch
LL was "blown away" when he found Bob did "Mama Said Knock You Out" on his radio show, and as LL left Philippe Chow in West Hollywood this weekend, dude told us, "What [Bob] needs to do ... is call me and let's do it together."

Times they are a changin'!