I have the bootleg cd somewhere. Bob Dylan and Johnny Cash messing around in the studio, and His Bobness sometimes forgetting the words. Still, it sounds like they had a good time. Oh, yes, one of the Cash/Dylan tracks ended up as track one, side one on Nashville Skyline. Not one of my favourite albums, but that has much to do with the way my life was at that time.
I can recommend Ring of Fire, That's All Right Mama, and, yes, why not, You Are My Sunshine. Plus, I Threw It All Away (from some TV programme).
Those tracks and the rest will, I suspect, only be up for a limited time. So, go for it.