I saw both the Who and the Clash that year (and The Dead for the first time) - not together. Those guys wrote some catchy punkish tunes.
I remember Joe Strummer saying something like - "If you don't want to liven up, we'll bring the Grateful Dead out at the festival in Jamaica." I found this on some message board about Joe Strummer and Phil Lesh:
"The Grateful Dead thing reminds me, in '99 Joe told me that back in '84 when the Clash and Grateful Dead stayed at the same hotel in Philly, Joe successfully drank Phil Lesh under the table. That seems like a union more powerful than NATO, no? Punks and Deadheads uniting in drink?"