Interesting. I suppose one would have to start with an election in 1790 and continue until the present day. Otherwise its impossible for us to know who won or what history is like. I suppose that Roosevelt runs in 1930 a year after the Great Depression and defeats Hoover more narrowly, his period in office is now 1931-45; Truman doesn't have enough time and loses to Dewey in a great year for the Republicans. From then on?
No, just the 1974 election is moved up two years. Everything else is the same.
As you said, it would be too open ended to have this start in 1790.