McCain would have won the 2000 nomination, he and Reagan were real close friends, and a Reagan endorsement would have carried alot of weight, enough to have other delegates sway McCain's way.
Who would McCain's Veep be? Certainly not Cheney, doubtfully Bush, maybe Lamar Alexander? Who ever it is would most likely get the 2008 nomination. If the economy still stinks and the administration is still very unpopular then the Democrats win in 08, if McCain does alright, then its likely a toss up with the DNC running someone like Hilary instead of Obama (I think Obama would not have ran if the administration was more popular, candidates usually dont get second chances). If the DNC run Hilary she wins in 08, Obama is a maybe but as I said I doubt he'd run, anybody else is a toss up.