Definitely a very different election. I think Snowe would have kept NH for Bush, and gotten him ME statewide, ME-02, IA, NM, and WI. With Nunn, two southerners running a populist campaign would have kept the Democrats Clinton's WV and MO, and I also think the ticket would have won Florida. Also, with another Southerner on the ticket, Gore wins his home state of TN.
There would be many close states, especially in the Bush column. Georgia would probably be the closest state, with Bush only winning it by 2 or 3 points. I don't think any of the following would have gone for Bush by more than 6 points, and many would be 4 or 5 point victories for him: Arkansas, Louisiana, Virginia, North Carolina, Wisconsin, New Mexico, Iowa, New Hampshire, Maine, Arizona, Nevada, and Colorado. Gore's closest states would be Pennsylvania, West Virginia, Tennessee, Florida, Missouri, Minnesota, and Oregon, most in the 5-7 point range.
All in all, I predict a funky map resulting in a 293-245 victory for Gore.