I think the assumption for '92 is that if Perot had been out for good, that most would've voted for Bush, Sr. (since it is apparent that Clinton, in a lot of instances, only held roughly the same, sometimes less, sometimes more, of Dukakis's voters), but I still think in a head-to-head matchup, Clinton probably would've eked out a win (because a lot of the Perot voters either would've stayed home or voted for Clinton in protest).
I think half the Perot voters would have stayed home had he not been on the ballot (which would have resulted in a percentage turnout similar to 1988), but the Perot voters who would have voted would have preferred Bush over Clinton by around 2:1, which would mean that the national popular vote would be around 49.5% each. That would result in Bush picking up at least GA, MT, CO, NH, OH, NV, WI, NJ (not a typo) and KY, with IA, CT and ME too close to call; for Bush to have won, he would have had to carry both IA and CT.