Moore does not have any specific actors in mind for these characters if the book is adapted for the big screen, but he does have some notion of the aural atmosphere of the adaptation:
Amazingly, I haven't given it any more thought than, "Something like the Billy Crudup film of Jesus' Son."Visit Radio Free Mike to learn more about Michael Scoot Moore and his fiction.
Not for any special reason except the kick-ass soundtrack -- I remember hearing that Denis Johnson got to pick the songs himself.
The Page 69 Test: Too Much of Nothing.