Tim O'brien (bluegrass/celtic/country) recorded an all Dylan cover record in 1996, on which he recorded Subterranean Homesick Blues. On tours that followed, it was Tim on mandolin and bass player Mark Schatz playing himself as a percussion instrument. He routinely introduced the song as the first rap song ever.
You may not have been the first and only, but you are in fine company.
Thank you!