Mountain (Leslie West, who also plays on a couple of tracks), Montrose (Ronnie Montrose), Hendrix, Trower, Free, Procul Harem (sp)....
seriously, I think the idea of appearing inferior to those guys really goosed him into some great playing. And because these are already proven good songs, its not like his usual crap of rounding up some nobodies and writing and recording an album in a week.